The secondary vacuum diaphragm is sticking when given gas. It doesn't do it when the motor isn't running. This is what I've done. Rebuilt carb (Done this many times on this and my mustang). Tried a different vacuum unit from another Holley. The spring and check ball are in their proper place. With the engine running, if I manually push up on the push rod it will stick. I don't think it can be linkage because it doesn't do it when not running. Or am I wrong? It seems to be a vacuum or it's not bleeding off correctly. Any ideas?