Marko, I have no idea. -5's on a 2.6 are still a bit 'meh' for my liking. Much better off with -9's/SS's. Having gone from RS's to -'s on a 2.8 it's the best thing I HAVE EVER DONE. I still feel like it lacks a tad low down grunt but the silly cams don't help. Put them on a 3.0 and OMFG. I have seen the graph (although not at full noise) and there is no comparison. NONE! If i build a 3.0 (and I may very soon) I can assure you I wouldn't put those things on the passenger side of the engine.
A perfect example is this. Last week out of UE there was a supra with a T04Z. Made something like 315 RWKW. Poor result yeah? Pitty he still had a standard cat and some crappy cat back. Any turbo setup needs the supporting mods to work. How many crap results do you see from -5's/2530's? HEAPS! Sort the setup out and I can Assure you.. i'll bet my car on it, that the setup on the street would be ruthless. 3.0, 2.9, 2.8.