Well that'* good it was that. When I had my issue it was random misfire.

Hi guys i am having a similar problem on my 2000 ssei. It seems to miss or sputter but only under WOT otherwise it runs and drives smoothly. I'm thinking it has to do with the coils any suggestions on how to test the coil packs? Help is greatly appreciated

Here you go. https://www.gmforum.com/trouble-shooting-test-procedures-141/testing-coils-spark-plug-wires-278818/

I'm gonna try doing this today ill let you know what happens. How much were your msd coil packs and where did you get them? I'm just curious if the would be worth getting in the future? Thanks again

Hey guys im still having problems with the miss fires on cylinder ONE. Me and a buddy changed coil packs for cylinders 1&4 and 3&6 because one tested out of spec. and the other was cracked. Pretty sure it is fuel related we hooked the car up to his diagnosis program on his computer and cylinder one miss fires at about half throttle and missed prlly 230 some time in less then 10 seconds. Driving normal there isnt any stumbles of misses. We checked the spark on cyl. 1 and it was good so we also checked the plug and it was white so means it runnings way to lean. today we also changed out the cyl. one fuel injector with an old one i had laying aroud it worked fine until the injector got warm so do u think that, that injector could be bad also? THANKS FOR THE HELP

Swap the injector with another one on the car. Then see if that miss follows that injector. If it does, the injector is bad, if it'* still on cylinder 1, then the injector is good. I would say pull the valve cover and inspect the springs. Last year had a car come in because of a bad miss. Checked everything. finally pulled the valve cover and found a broken exhaust spring.

Compression is good also

Compression was good on the broken spring. The only way your going to know is to actually look.

It still has a miss fire on cyl 1 we swapped the injector with cyl3 and we pulled off the vaulve cover and all the vaulve springs looked fine. Thanks for all the help again

OK, so you changed the coil, the wire, the plug, the injector, and inspected the springs. That really starts knocking down the list of possibilities. There could be a problem with the injector wiring, or a chipped piston causing bad predetonation.