I have a similar issue with my car, exact same combo as the OP, but greddy profec boost control. Rev too high and the boost alarm goes off. It's limited to 1.2, but goes up to 1.6 (not spiking, goes up and stays up). My engine check light also flickers (possibly just showing knock? I dunno). It was also perfectly fine for one month after the GTRS was installed (just recently), and now I'm getting this 5h1t. I hate not being able to put my foot down
My car goes in for looking at (Trojan too!) very soon, I'll keep you up to date. John already had a fiddle with the boost, but it made no difference. Strangely, he says he has no issues with it on the dyno, yet I can make it happen whenever I want (ie rolling in 4th doing 60kph, then put your foot down - BAM, warnings/alarms). I'm sure he'll see it this time around. I'll be watching this thread.