[Rich72C10]

I agree its a vacuum leak, Quadrajet Power more or less said the same thing.

@Rusty - I used a brand new base gasket (and it's one of the thick / good ones) on Wednesday. I was not going to reuse a $5 gasket, plus they provided me with a new one. I actually have one or two more new ones in stock! I never want it to be a question about a gasket.

I did however reuse the "whistling" carb gasket when I installed my old carb about two hours ago, on purpose. No more whistling and I am back to normal driving. I do need to tweak things because I left my timing higher (they suggested I bump it up). Also I know my left mixture screw is not right as I took it out and eyeballed it back into place yesterday (long story why I wanted to look at it).

So either this carb has been modified so much that my engine can't handle or I got a bum rebuild...