Does the pedal return?
Any CEL?
Dirty throttle body?

 

Since this really had nothing in common with the thread it was attached to, I dstarted a new thread.

 

I had the same issue, here's the thread.

https://www.chevyhhr.net/forums/prob...-issues-50825/

 

I have had the same issue since new on my 08 HHRSS Manual. Seems to do it worse when the engine is heat soaked, like in a drive thru line then leaving. Rpm's hang high after the throttle is released for a couple of seconds. Did it before and after the Stage kit install in march of 08, does it now but a bit more often at 91,000 miles. I have replaced ECM, ECM Program, throttle body and throttle position sensor, gas pedal assembly and electronics, MAP sensor, and checked all lines and hoses. Seems like its something in the ECM programming, as an emissions cycle or something. Have not been able to find anything else. SS runs great and has has no other issues. If anybody else finds the cause please advise.

 

As noted in the thread I linked to, the problem has not returned for me. Try swapping the brake pedal position sensor with the clutch pedal position sensor, or installing a new clutch pedal position sensor. I think that's what fixed mine, or it just coincidentally fixed itself.