stock boost was 11 ish i think....you can get the boost a bit higher but the stock turbo/ cooler combination isn't good for a lot more power..
on stock rods and pistons a TD05 turbo along with some bigger injectors and fuel pump upgrade
14 is still safe but needs a chipped ecu /tune
15 stretches the friendship if the tune has any knock...having said this, there are guys running a lot more than that but have spent some money on refining a good tune.