removing cat converter...

[Max777]

Well, I'm no expert, but as I already said, the reason for overboosting on a stock application when you change the exhaust is the lack of flow through the wastegate... the turbo is freed of a restriction, therefore it makes it's natural boost a lot easier. At this point, the factory wastegate actuator sees that the pressue has gone above 5~6 psi that it is designed for, and opens the wastegate bypass. However, since it's not big enough, this does not drop the turbine pressue enough, and you end up with boost hitting 8+ psi, at which point the factory fuel cut shuts down the engine...

With your setup, as I already said, it is not a concern. Why dont you take the cat out, and just see for yourself? You have a big wastegate, so flow should not be a problem, you have an aftermarket ecu so you dont have fuel cut anymore.

All that removing the car will do, is make the turbo spool FASTER, and yes, if you ran no wastegate, the pressure would be higher, but since you do, it will bleed off extra exhaust flow to the turbine once it hits the preset level, and stop if from going over.

Brian at BNR turbos ports the stock turbo wategate to roughly 38mm, which can handle 400hp, so I am making a guess that your setup should be fine.