slavevo

So Ive had my 2011 Evo x for over a year and a half now. Got her at 65k (km since I live in Canada), shes now at almost 90k. Previous owner had a HKS catback exhaust, an AEM intake and a COBB BOV along with a boost gauge and the COBB AP. The tune he had was stage 3 91oct which I had been running for a while. I didn't know too much about tuning as its my first turbo car so I didn't want to play with it and left it as it was. On the stage 3 it hit 27psi but I rarely WOT because of the city traffic so it didn't bother me too much. Up till now, I haven't had too much money to buy parts or time to do research, so I've been driving it easy. Since I've actually saved up some money now to get a few parts for it, I decided to actually try stage 2 on the COBB AP. Ive been reading a lot about what people are running here and 27 or 28psi is quite a bit I thought. So I flashed the ECU to stage 2 91oct and at WOT boost spiked over 30. Did a few pulls from 2500RPM in second and a few in 3rd from 3000RPM, same thing. Scared the crap out of me, I mean car feels amazing but overboosting higher than stage 3 which I thought was weird. Tried stage 1 91oct, same thing. Finally I set it back to stage 3 91oct and it hits a max of 24-25psi now, before it was 27-28 on the same tune. Can anyone explain why this would be happening? Is it safe to go back down to stage2, considering stage 3 requires a test pipe and EBCS and I have neither.