Here's what I've had to do on one Edelbrock intake that wouldn't seal. I used Ultimate Black RTV, put it on about 1/8" thick, let it set up overnight before installing intake. I had to push down on the intake to get the bolts to start but once I did it went on with no more vacuum leaks. Some intakes get through quality control that should never have gone out, but things happen. Give this a try, I think you'll have your intake sealed up.