95 Riv, antifreeze filling plenum

I have 95 Riviera that antifreeze is being sucked into the plenum and then into the cylinders. I just replace the gasket with a new one and it's still doing the same thing. Does any one know the tork setting for tighting the plenum bolts? Or has any one had a problem with this that requires something other than new gaskets?
Thanx for the help!
Don

Standby for a new intake manifold, if your issue was like mine. Ended up losing anti-freeze, into the cylinders. Replaced the gaskets, same problem. After round 2, took very close look at the intake and found problems with the EGR passage; it had actually melted the plastic intake! I replaced it with a new GM intake and no more problems :2cents: . This happened about 4 years ago, and I think I have the old intake and can send a photo if you want me to.

I found the problem the heat of the EGR tube had melted the plastic plenum and water was being sucked into the engine in the intake. I had to replace the Plastic plenum and it no longer leaks.