GTSBoy

Perhaps unsurprisingly, there's already a whole thread on that topic, which should go at least partway to explaining my slightly flip answer.

There are no vacuum lines associated with VVT. It uses angry pixies and compressed slippery.

You want at least a GT35 sized turbo. The VQ25 turbo will be damn near on boost at idle and out of breath at 4000rpm. Not good.

Should have put a handful of confetti & glitter in there.

Under the inner pivots of the front lower control arms. Nowhere else at the front end is safe. Not under the crossmember. Not under the chassis rails. Not on the side rail jacking points. If your chassis stands are too fat at the to to fit on the pivots, get the angle grinder out and remove some metal from the stands. Under the inner pivot at the rear too. Almost nowhere else is any good at the rear.

Well, obviously you can't put the Z32 onto the stock ECU, so unless this was specifically for one of your ECU upgrade options, forget about it. I would not install shitty old 555cc injectors into anything these days. Man up, buy 1000cc ish Bosch EV14 based injectors (or Siemens or Denso, or anything of the same vintage as EV14s) and win at life. Better spray pattern, much much better spray at low pulse widths, even though they are double the size of the 555s. Also, much more headroom for E85, The potato is famously mismatched for an RB25 unless you really only want to have what you have now (which is a responsive street car that falls off at the top end). It might make a bit more power than it does now (given an ECU, some more boost, and possibly the E85), but the back end is really a restriction to how far you can go. You should just search on these forums for the many many posts on what it is good for. A street turbo that boosts fast, but not a high power turbo. Keep in mind that it is half of an (upgraded) twin system used on GTRs....basically the same engine, but only half the turbo. E85 will certainly help the chokey rear end because it reduces exhaust temps. If you want E85 only, the PFC is the easier option, as you just buy it and plug it in. It can't do flex, but you don't have to source an RB20/VG30 ECU, do the extra wiring, etc. If you want flex, your only choice (of the 2 options) is Nistune. Yes, lots of people are running flex off of suitably feature packed Nistune ECUs. As if you would not buy a bloody Consult cable and a Nistune license if you were going Nistune!!!!! Would anyone actually consider living without it? Many people have experience with both. It is very clear that the Z32 ECU is not a great choice. It works, but it is just not quite right in a number of ways. The R32 ECU can now be made to do absolutely everything that is needed for an RB25, and so is the clear standout Nistune option. Yes, but I would not go to the expense of setting up for E85 for a small turbo application. The returns will be too small to justify the cost. You want more power? Put on a bigger turbo.

Also, have a look at Performance Forums, for postings going back a few years now by Nelsonian (or some name like that with numbers on the end), talking about considering and then actually doing "cheap eBay aero" on his fast Falcon Turbo. IIRC there is a lot of very good learning in there. The upshot is that what Hardsteppa said is true. The eBay aerofoils can be fine. Ultimately, all this learning already exists anyway - you just have to dive down the rabbithole to chase it. There was massive work done by NACA on aerofoil profiles and there have been numerous studies of how each of these perform when used upside down (ie, on a car), with lots and lots of "if you're doing A, choose aerofoil B. If you're doing X, choose aerofoil Y" type advice available. Just have to search it out, and maybe buy the occasional actual paper book.

To be fair, 98.37% of the Australian driving population are completely stumped by them also.

The usual answer is "don't take it on unless you are able to do it yourself". Perhaps that's less so for gearbox conversions than turbo engine swaps, but it's been the usual advice. However, where there are availability issues and the price difference is that wide, sure it's practical. I did it to my R32 many many many years ago. It's not difficult, just need all the things and enough skills to make the wiring changes, etc.

Also, question.....which bearing is stuffed? The fan is bolted to a hub that is on the front of the water pump. It's not a shagged pump we're talking about here?

This. This. A thousand time this.

Almost certainly running lean & therefore very hot EGTs. The hot exhaust makes the dump pipe overheat the firewall & air-con hoses etc around that part of the engine bay and it stinks.

Yes, well, you can't run a Z32 AFM against a standard ECU without Nistune, correct. I would suggest that your IACV would be dirty/sticky/blocked, hence the engine's inability to control revs. But all the roughness could be just about anything. AFM (dying, dirty, broken solder joints), CAS (same), injectors (dirty, broken loom plugs/pins), coils (same). The list goes on.

Well, if it worked before, and you're sure that you have it back together correctly, then the options are; You also messed something else up when you put it back together, which is difficult for us to see from here, or Perhaps having the hoses the wrong way around has caused the variable manifold butterfly to jam (from being driven in the wrong direction perhaps). Can you try to apply vacuum to the hose that should have vacuum and see if what is supposed to be moving is actually moving?

Is that code as translated by some dodgy reader, or from the manual?

As if you only have to buy from the UK. You could get it something direct from Japan, you could probably call Quaife (if you wanted a helical) and get them to make you one right there in the UK. You could go and watch them make it. I wouldn't weld a diff....too crudo 1990s stylo for me. Horrible to live with too. As I said, do it properly, or don't do it at all.

Shimming VLSDs is stupid. Do it properly or don't bother. Just get a 1.5 way Nismo GT Pro kit.

They're the same car at the chassis level.

Not supposed to be different R32/A31 https://justjap.com/genuine-nissan-coil-pack-loom-nissan-hcr32-a31.html

How long is your piece of string? Copies can be anywhere from perfectly fine to absolute death traps. You won't know until you find out. Hit a small rock on the road and have the rim come apart? Possible. Have the thing go out of round because of poor metalllurgy? Possible. Have it be 50% heavier than the wheel they copied because the copy shop doesn't have access to the techniques used by the original? Possible. Or it could be damn near as good. Luck of the draw.

Well, there's also the question of "What category do you want to win?" As it stands, the question makes no sense. You did not specify "just a plaything". Nor budget, nor prep level of rest of car, as per JGTC's point above. As such, my vote is the max option on your list.

It's a stepper motor. If you unmount it from the plenum (and block the holes/pipes it was connected to) and leave it plugged into the ECU, then it will (should) follow the ECU's command to open and close. If you run the engine and set the idle real low, the ECU should try to open it up. There should be little resistance to blowing through it. If you set the idle very high, the ECU should close it right down and it should be quite difficult to blow through it.

Does the IACV work? Is it clean and the valve moving?

AFAICT the only one worth buying is the Tein kit.

Never heard of them. Not a good sign.