NYRDRMSS

Lately I've been having an issue with the engine RPMs not wanting to fall when off the throttle in my 2001 SS M6. For example when you downshift a gear the car will normally decelerate, the lower the gear the more your speed drops. But lately when downshifting the RPM's jump up to match the lower gear but never drop much and the vehicle will maintain speed to the point where I'm not slowing down at all, even though I'm not touching the gas pedal. It seems like the car is getting just enough gas to keep the RPM level the same. Basically I can be running in 5th gear at 55 mph then downshift to 3rd gear and maintain my speed above 45 mph for like a half a mile without re-accelerting. The gearing does pull the speed down some but it almost feels like the engine is working against the gearing to speed it back up. Where I really notice it is if you are braking when still in gear, you can feel the engine pulling forward still against the brakes but only a small ammount like maybe around 1200 RPMs worth of power but just enough to keep you moving. However the engine idle never been high at all, always idles fine with no problems until giving it gas the problem only occurs while driving never when stopped. In nuetral you can give it gas and the RPM's go up quickly but seem to drop very slowly but never sticks just seems to take a while fall all the way back to idle. I have cleaned everything trying to fix this issue: TB, IAC, TPS, MAF sensor, air filter, TB does not appear to be sticking, throttle cable looks fine, I am out of ideas. Any help would be much appreciated.