Have you checked to see if you are getting any codes? I've had problems with poor performance and it was the ICM. I cut and pasted a reply from a previous post I made some months ago.
The MAF was replaced (due to code (E034) and then I got a code for the Cam Sensor (E041). Replaced both which were of no help. I then got a code for the Ignition System (E042) and after checking and finding that two cylinders were not getting spark, I then replaced the Ignition coil and ignition control module. The car now runs great (at least for the 25-30 miles that I've driven since). Turns out, I suspect, that the ICM was probably the original culprit all along in spite of the E034 and E041 codes. Funny thing is that the codes popped up one at a time and not all at once. Had the E042 code shown up first, a replacement ICM and coil pack may have cured the poor performance right off the bat. As it is, I spent way too much on trouble shooting, especially with the replacement MAF (and also the catalytic converter) before checking the ignition coils. I'd suggest that anyone encountering extremely poor performance start off by testing the ignition coil and ICM.