I bought a single vacuum/pressure gauge today and tried to get a good read on my carbs, but at idle engine speed on carb #4 (the standard) the manometer needle just kept jumping from a vacuum of about 9 to a pressure of about 7 rapidly. It wouldn't stay put on any single value. I hooked it up to the other three carbs too, and the same thing happened. However, if I revved the engine to about 5K the needle kind of leveled out at about 8 (vacuum), but was still a bit jumpy. Just wondering if anyone else had this problem and if it's a vacuum system problem or what??