The GTIR engine is a little different with having quad throttles, but this wont affect what you are currently having issues with.
I have used a nemu in a P10 ecu, jdm, which is not listed as being supported, and it ran fine. There are some differences with outputs that the b13 ecu has, but the address for the fuel/ignition etc and all the basic running important stuff is the same.
I think you are more likely to have a mechanical issue with a sensor or some such, maybe bad fuel pressure regulator or vac feed, maybe a air leak in your intake tract? CHeck your maf, check you have the correct maf chosen? I have a z32 in my car, blew it apart with blow thru and taped it up, then got a spare so fitted that and the car wouldnt run, it was a N62 z32 maf still, but for some reason the Maf curve was different.
Make sure you dont have a leaky injector or something silly too.
Check every earth, engine to chassis, and the 2 under the intake manifold, many people have had odd issues and said yeah they are fine, then found one is a bit loose or has some corrosion.