My car bucks when de-accelerating, and has alter idle issues?
 

My 85.5 944 has had this problem since I've owned it (3 monthes). I've changed plugs/filters/belts/seals/cleaned all the intake system. When I cleaned the TB, I noticed it had alot of sludge build up. I cleaned it very well, and reset the computer. Started it up, and after it warms up it idles at about 1150 rpm. Every once in awhile it goes to maybe 950 rpm. Also..everytime I let off the gas, it kinda jerks around 2-3 times then smoothes out. Never happens upon acceleration though (unless my autothority chip is installed). Any ideas? I thought maybe I should play with the idle screw, but the fact that it doesn't always idle that high kinda confuses me.
Thanx,
Greyson

Clean and set the switches on the throttle body.