6 or 9psi? And odds of blowing head gasket?

You already know the answer to this bro.

It's all in your tune and the ability of your fuel system and injectors to provide the correct AFR.

Head gaskets don't just blow because you upped the boost to 9psi unless you fail to properly tune for the added air.

Do the 9 im running 10 pounds now no problems that i know of. If you drive your car like you stole it 6 pounds will cause you problems too.

928motorsorts is who rebuilt my PD the last time, and I haven had a problem since. I had the 2.75 pulley put on the charger and had the car retuned. The tune ended up being rich from 5200 to 5600 when the pull was stopped. There was only 19 deg. of total timing at 10lbs of boost so the tune was plenty safe. I was about 2 months later and my stock head gaskets blew. Theu blew out from the upper water jackets to the fire ring on 3 cylinders on both banks. General consesus from info on this site and some good tuners was that any thing over 6lbs of boost should be using head studs. I showed the gaskets to my friends at CD Race Cars ( they have a mustang that runs 7.00's at 203 mph ) When they looked at them the first thing they both said was that the heads were lifted under boost with the stock head bolts. They said that anything over 6lbs should be using head studs because the heads only have 10 bolts, and that head bolts dont have near the clamping force that head studs do at the same torqe. If I were you I would put a set of head studs on the car If it doesnt already have them. If it does then make sure it has a good tune and you will be fine.

Those guy's gave you the right answers. Good head bolts are important. Studs are better and why not replace them when your doing head gaskets. Make sure the mating surfaces are flat to ensure a good seal. I'd go with larger injectors at 9lbs and your fuel pump is a bit on the small side. Running lean will kill a gasket with no boost. It's better to be fat than lean. Get it to a dyno and have it tuned it's well worth the money. Tune, Tune, Tune. I really think things don't wake up until your over 10lbs anyway.10lbs has always been the minimum amount of boost I played with. When I was young I ran a B&M roots blower 30 Ford coupe(like the one in American graffiti) I blew a set of gaskets every week it seemed like. The only good thing was I learned to do them in less than two hours because the motor was so easy to work on.