Intake manifold leaks (3 TIMES!!!)

Hey yal,

So heres whats up, over winter we built a 1969 firebird with a 400ci chevy sb. This is a strickly track, drag car. The engine dynos at 330hp and 470torque (at the wheels)

Since the car was built we have had problems with the intake manifold leaking, so far we have replaced it 3 times. Last time we replaced it we check the gap between the intake and the block im not sure exactly how much of a gap there was but it is pretty signifigan. The intake that came with the engine is a "sports man" or something.

Ive herd that since the heads were running have been "shaved" that messes up the geometry between the heads and the intake therefor forming the gap that we know we already have.
it has been sugested to us to have our intake mechined for a snugger fit, our plan is to do that this week once we buy our new intake (victor jr).

I guess my question is what else could be causeing these leaks, obviously if theres a gap between the block and the intake thats a issue but the last time we repaced the gasket it helt for 4 runs on the track (12.3-12.8) and 4 dyno pulls... then we decided to put a PCV valve on it to relive so of the extra pressure in there (we haddent been runnin one before) and then first run it blew the seal on the way back to the pits.... WTF!!! a PCV should have helped relive the pressure right?

I believe we are going to have to shave the intake manifold and in that case we will buy a victor jr. but Do you guys think that is our problem?

Should we be running a PCV valve? up untill last weekend we had 2 K&N vents on the engine...

any help would be much apprishated,

Thanks guys!