only been making that power for a few months now, and i havent been driving it all that much to be honest. my current wastegate is faulty and has some eratic boost pressures running through the engine because of it. so its not something i have been pushing til i get the new one and know for sure that only 18psi is going to run through it...
i do get the issue of stalling since im running a atmo bov, havent been arsed to work out a plumb back system with the aftermarket plenum... but thats an easy situation to resolve with some taps of the right foot.
known a few cars that run up near 18psi on smaller turbos and only making 240-250rwkw so it really looks like the bigger turbos are able to give the engine the extra air they need without pushing the limits of boost and the CR.. that said i am sure the cometic metal gaskets dont change the CR at all, but are more likely to hold up with a little more puishment than the std ones.