Don't over torque the bolts and as gtow69 said, follow the correct tightening sequence.
The torque specs for those bolts is much lower than what most people expect it to be and overtorquing causes the manifold to seat incorrectly.
The torque is 30 lbs for center exhaust bolts,20 lbs for end exhaust bolts and 35 lbs for intake bolts I think, but that should be verified with automarc or someone with a shop manual.
The set rings for the intake manifold should be ground down to compensate for the amount that was machined from the manifold.
Hobert
