we run 14-16psi, but that is with forged pistons and steel headgaskets and a front mount intercooler with watersprayer (plus it is a rally car) A friends leone was running a top mount cooler, with a legacy turbo and consistently running 18-20psi boost, with std pistons and internals. That car ran 3 seasons without a major rebuild. It think to stop the cut there is a boost switch by the drivers side strut tower you can disconnect that will stop the boost cut. Running 14-16psi we have no problems with the car leaning out, if anything it is over-rich. I know someone said something to me about it, and mine doesn't have it.
cheers
simon