change the lot: belt, idler, tensioner, cam seals, crank seal, and water pump..
save money buy buying a major service kit for about $400 then pay a mechanic to install it to avoid the mark up.
it's a sad reality, but R32/33/34 Skylines GTS-t GT-Rs are pretty much all siet boks compared to newer cars.. heck a Ford Focus RS would munch hard... imagine a basic modded Ford Focus RS.. would clean up a a GT-R with 50k worth of mods.
Stock as a rock EVO does 1m10 around Wakefield on rubber out of the factory.
Now imagine with a basic dual map tune, 280awkW stock turbo on E85 with semis.
Pretty much two options from my personal experience.
1. Set the AFM to Z32 and click on half value (if running 2) and adjust k value till your car hits stoich with o2 feedback disabled
2. Leave as is and adjust the k constant till you hit stoich on idle with the O2 feedback flag disabled
The beauty of the Nismo or Z32 etc. Is that the curve is nearly stock so there's no fancy calibration need like the HPX afm which I've yet to use.
If you think outside the box you can piggyback a full standalone ontop and let that ecu do all the work but the stock ecu for auto control. Then literally cut all the ignition and injector outputs from the stock ecu and wire it up to the standalone.
Always ways around it, just need to think outside the box. Also you can set the stand alone to input a gear change signal and retard timing for you so you don't grenade your box.
Lol turbo kit will cost as much as your car and offer the same performance as a high flowed hypergear turbo if not worse.
I suggest you do some research.
That's pretty poor form from a tuner.
Could also be mixture related, once you get a wideband on, it should provide you with more insight on what's going on.
Close to stoich or stoich on a cold motor, will stall, too rich on a cold motor will stall.
^ you're better off using an external gate with a weak spring to emulate what Tao is doing with that flapper. A few guys have done that (not here) but Google!