Bouncing RPM's
 

I've got an M6 with all the mods listed below. They have all been on the car for about a year and a half. The problem started a few months ago but never thought to much of it, now it’s just annoying. When I'm driving everything is fine, and when I'm stopped the car idles fine. However if I am driving and push in the clutch anywhere from highway speeds to 30mph just to coast the RPM’s will bounce. They hit about 550 or 600 and then jump back up to 950 and it will do that repeatedly until the car comes to a complete stop or I put the clutch back in. It has never dropped lower than 500 or anywhere close to sounding like it is going to die. I have no throttle body work or MAF work. However could one of these be dirty or need some kind of work?
Thanks!

you can clean the maf with rubbing alcohol and a qtip

Think that would do anything, or just a starting place? Also it doesn’t do it all the times, but still enough to be noticed.

TTT....no one else has heard of this?