RPM gage is going up and down
 

I have a 05 Durango and I noticed in the last few days my RPM gage drops low and jumps up and down and sometimes in park the rpm will drop so low that it cut off...one mechanic said it may be the vacuum hose. I have to ride with my custom stereo off if just to keep the rpm a little bit stable but still have the problem but not as bad.

Sounds like a TPS.