My 88 wagon has a wierd problem. When idling cold it idles great after driving maybe 20 mins the idle seems to stutter. There is also sometimes hesitation when driving away. The other day it was so bad no power after stopping at a light I could only get it to 20km/h I had my foot to the floor and then boom the car shot forward and drove again.

If I put the car in neutral and rev really high it also seems to misfire as well. Shakes violently. Fortunately I never usually rev it so high. Any Ideas.
It seemed to happen after I flushed the power steering but some of the fluid got on the outside of the AMM also down below the reservoir. Not to much on the AMM though. I took the AMM off and there did not seem to be any inside it or on the screen. I do have the adjustable kind and have tried leaning the mixture with no luck. I also recently used some fuel injector cleaner in the gas tank.

I replaced the spark plugs last night with no luck. I tried disconnecting the IAC to see if it was sticking open and it didn't make a difference. Also I disconnected the AMM and the same result.

Anywhere between 1000 and 4000 rpm the car runs great. In actual fact after I spent $40 canadian on the Bosche Platnum +4 spark plugs it runs awesome when cold. I can actually peel the tires. But when the car runs for more than 15 mins it idles rough and hesitates again.