The problem is crappy kali gas....91 ocatane(maybe
) is NOT condusive to high boost.
Just because the turbo will hold xxpsi boost dosen't mean that it can be tuned to that on a car with crap gas.
Pour a couple gallons of toluene or xylene in the tank and see what kinda tune you can get...I guarante it will be better....but then ya gotta run it all the time...
So...junk kali gas is the problem, I'm sure.