rick from synergy made 840rwhp with his 5.3 with 317 heads on a set of twins i think 18psi

a motor is an air pump, you toss in agood cam and heads with a effiecent turbo with a good tune and youll see numbers.

you need to wine a smaller motor out to produce the power of a larger motor with same turbo. the turbo needs to spin fast, faster it spins more power it makes. look at 4bangers for example small motors with large turbos and produce some serious numbers when they spin some rpms. granted its a ticking timebomb but will make power.

a forged motor and stock motor in the end will make same power but which one last longer is the question. a forged motor is made little stronger so it doesnt fail as fast. it can withstand the abuse. a stock motor fails faster cause of bad tune or even just overpowering its parts.

a forged motor will live little longer behind a poor ass tuner, a stock motor will fail the first pass with a piss poor tuner. with that being said with FI you need a good tuner and tune it smart.

the last time i had truck on road it was 15psi no meth 18* timing AFR of 10.8. ive seen 18psi with same timing, my motor hasnt shown any sign of failure. i check plugs, oil, compression and leakdown constantly

with this being said a 5.3 with a 76mm turbo will see 650 if in the right hands, if in the wrong hands then well...go read the net for those failures