I think I may have a problem, but I want to check. At idle, you can hear the cars exhaust kinda "breaking-up" kinda like if were missing, but the tachometer nor datamaster shows a miss (looking at the rpm). After driving the car around for a while (like 30 minutes of lots of stop and go traffic), the car has a slight "vibration-like" feeling while driving. Like its not running smoothly. Mods in my sigiture, ANY suggestions would be greatly appreciated. I know its hard to say what it is like, but that is the best I can do...

 

If the problem shows up at idle AND it's a cylinder misfiring, it will show up at the headers. Use an IR thermometer to check primary temperatures from dead cold. See if one is lagging all the others.

 

Excuse me for my lack of knowledge, but do you mean an Infrared Gun? Where can I buy one?

 

Summit, Jegs even Sears has them.