97 mag mpi 502. Stock with exhaust, fuel system and an M3SC inter cooled Pro charger kit. Running 5/7psi now on 91 octane. I've got 110 available here, if I ran the gas, what kind of boost could I push the motor to without worrying about it letting go?

Stock head bolts and gaskets, I'd say you're living on the edge at 7lbs right now. You want more boost, I'd consider some MLS gaskets, and head studs. Just my opinion. If you want more power, I'd def lose the baby 502 MPI cam for starters.

Does the stock 502 cam have a slightly rough idle? Mine does but I know stock big block pickup motors idle baby smooth with there peanut cams..... I'll leave the boost alone then but will do the better gaskets and studs if it ever let's go. Thanks!

You are right on the edge now with injector. I would bet that it is at damn near 100% duty cycle with that much boost. I'm actually surprised it hasn't let go yet.
Eddie

Assuming, Modern engine management, (holley efi) bigger injectors, proper cam, better fuel, studs and mls gaskets what can the bottom end take?

Quite a bit actually. I wouldn't take it past 700 or so. You are probably playing with fire beyond that. That's my opinion, at least. I prefer to error on the safe side. It could withstand more in shorter bursts, but if you are talking about running at will, then I wouldn't go much past 700 or so.

My 502 has built bottom end and some head work, im right around 700 hp. and mine did idle rough, i think because of no thermostat and engine not getting to operation temp. I have m1 procharger and intercooler. we tuned the low end took a little fuel away and seems to idle much better.

I believe he is running factory Procharged set-up that just uses the FMU and no computer programming. Which i don't like.

Thanks for the info guys. My setup is NOT factory, gues I could have mentioned that.. My ECU was calibrated by Arizona speed and marine back in 2004. I have the M3SC pro charger kit with remote mount inter cooler.

With a forged bottom end I assumed it could handle quite a bit of boost as long as it didn't detonate but I'm no Chevy guy.. Makes sense that the head bolts and gaskets would go first. Unlike my BB Fords, the Chevy head bolts protrude in to water jackets so there not as strong..

502's don't have headbolts that go into water. Another plus for the 502's. Chevy did a decent job with them.