So this has been going on for quite some time, maybe 6 months. It hasn't been an issue, I like the sound and feel, but I should probably find out what is happening. My car has nothing done to the engine performance wise. Just a crate motor thrown in with no bells and whistles. Now it will always have a varying idle that jumps around a bit like you would see on a car with a performance cam. It also sounds like it too; I am always asked by car guys what kind of cam I put in it and they are always shocked when I say none.

Is there anything I should be worried about here? I can try to post a sound clip of the car so you guys can hear it.

 

Sounds like a potential vacuum problem to me. Could have a cracked hose somewhere or something of that nature.

 

Agree with delta, also check plugs, wires, cap..