Quote Originally Posted by R055IE View Post
Does seem weird everything was fine till the exhaust went on ?? , surely the throttle body cant be stuffed ??

the must be plenty on here that run 3" full exhausts without issues ??
Yep, but a some only from the dump pipe back and Fwdpatrol is correct in that purely from an engineering view 2.75 is optimum...

Anyhoooo, fooling around with boost is treating the symptom not the fault IF the TPS is dodgy.
You could see if resetting the fault code makes it go away in that it may simply be a latching fault code and the TPS glitched and is actually OK and you do really have overboost issues triggering limp mode.