Just want to know if I still have to clean the barrels before closing this. Still waiting for the gasket. Any recommendations to make sure the process is done properly. Thank you

 

just make sure both surfaces are as clean as possible, and there is no gasket material on either surface. I recommend using the copper spray sealer, it is very sticky and seals surfaces like this very well. Have had upper off for coils on mine and head gasket on sons, and neither have had any leaking issues.
just a thought

 

Last time I had my manifold off I sprayed the insides of the tubes with brake cleaner. It was mesmerizing because so much oily stuff came off. I used four cans.

I guess that is from a bad oil separator because I can't imagine how else oil would be in there.

It didn't make any difference in the way the engine ran.

Also, the copper coat gasket compound is amazing. I re used my plenum gasket, coated with the stuff. A big no no. But no leaks and I didn't have to wait.