vacuum gage needle vibrates

[greg0380]

I have been driving around with a vacuum gage hooked up and noticed it is not steady or smooth. SOMETIMES at idle it will vibrate and pulse, enough to make the gage humm, and other times it is realitively smooth with a slight wander. THe vibration of the needle is less than an inch of vacuum, and when you give it gas and the vacuum drops to 0 the pulsations are still there. I have tested teh gage on another vehicle and the gage checks out fine.

I am thinking sticky valves but don't have any experience with thaat type of provlem. Anybody have any ideas? I think if I can smooth out the vacuum the truck will idle better...It has a stock cam (I put it in, nothing radicle), it pulls 20 inch of vacuum at idle and has TBI, the heads were rebuilt 2 years ago.