Sounds like a plenum gasket or intake manifold gasket.

 

This is why I overlooked the plenum gasket hydra. However thinking about it, if you went with another stock plenum gasket, this could be the problem again. If this is the case again, go with a Hughes Plenum Kit. This is always what you should do to anyone seeking further advice on the subject also, never go with a stocker.

http://www.hughesengines.com/Index/p...p?partid=26190

 

Thanks for all your help. I will try to do a leak down test this weekend and I will keep you posted on what I find.

 

I did purchase the Hughes plenum cover and gasket. When I pulled the old plenum gasket it was not blown out at all, I still changed it out though.

 

For those who need answers later, I found the cause of my vibration. It was my harmonic balancer. Its neat how you ask for information about a certain issue and give all the info you can and then people try to fix other issues other than the one you posted about.

 

Ya,

Things tend to get off topic sometimes.