Intemitent Ignition Problem (HELP)

[Shadowyng]

My girl is not feeling right lately. It starts fine but then after five minutes of driving I start getting problems. Once I'm on the highway and hit about 80-85 mph the car will studder. It seems as if the enitre ignition to the plug turns off and on quickly. It only happens after the car has warmed up. And after while waiting at stop signs the car idles irratically and then often stalls. I brought it to the shop and there are no codes coming up. All sensors are reporting the correct ohms as per the manuals. I got a sneaky suspicion what the problem is. Just want to bounce ideas around and hear is anyone had the same problem ever!!! Any help would be aprriecaited guys. I have a 92 LSi touring. Thanks again!!!!