Originally Posted by davestx

I have not checked the compression but the spark plugs, wires, cap and rotor are fairly new. will pull a few plugs and see what they look like. The coil is older. The ECU is from a 560. To reiterate, the car has never run smoother since I changed the ICU the other day. Everything is perfect until I try to accelerate hard in the upper RPMs. It will get to the redline but just much slower than it used to and with an occasional buck. I read in another post that throttle linkage is sometimes the culprit. I will check that tomorrow or Monday. I will also check the air filter. It has been a while since I changed it.

I changed a number of things in the last few months trying to get the idle straightened out.
1. injectors ( it just occured to me that I did not change the seals because I did not have new ones handy. Could that be it?)
2. EHA. I damaged the one that was in the car but had a spare (untested) . can the EHA cause this symptom?
3. ICU. Can the new ICU somehow be causing this problem?
4. Fuel filter
5. Accumulator

Where does the signal from the throttle switch go? Could the signal not be making it to its destination?

Could something with the timing advance cause this?