Engine vacuum does drop as RPM's increase, so could be a vacuum leak, but usual telltale sign of vacuum leak is wandering idle. Try spraying carburetor cleaner at all strategic points around engine (a little acetone isn't going to hurt anything). You need the kind with a straw for point pinpoint accuracy. If you've got a vacuum leak, engine will rev up when carb cleaner hits it. If not, you'll at least have a cleaner engine. Note that carb cleaner will remove all your silicone. My idle speed motor fails open. If yours is similar, that shouldn't be the problem. Have you tried isolating motor from the idle circuit (big vacuum lines, not electricity) and setting with screws in the air/fuel assembly? If it weren't for my A/C compressor that would be my preferred method. Check your spark timing. If the spark advance diaphragm is receiving vacuum at idle, your ignition could be WAY advanced. Makes sense that timing wouldn't return to normal until engine vacuum drops. Car will run just fine without spark advance, so you could disconnect during problem diagnosis (don't forget to plug the loose vacuum line). Did you tinker with the fuel mixture? Could be too rich until car gulps some serious air. You might try disconnecting power from both cold start valve and warm up regulator to ensure neither has gone crazy (would also enrich). Good luck, Bill Robertson #5939 >--- In dmcnews@xxxx, "Payne" <bpayne@xxxx> wrote: > Thank you for taking an interest in my problem! The reason I haven't posted any update is because I'm still waiting for a part. I have got the new gaskets for the "W" pipe and am replacing some vacuum lines. > I just have one question that someone may be able to clear up. Right now the car has very little power below approximately 3,000 RPM. As soon as it gains in engine speed, she feels like her old self again. I thought I had the vacuum leak fixed, but is this even characteristic of a vacuum leak? > > payne