Engine Cuts Off Randomly...?

I've had my 03 for about a year now and every once in a while the engine will cut off. It has happen wile i was on the highway just as many times as it has going through a parking lot. The cars current only mod is 40s flowmasters. Can somebody please tell me how to fix this problem? I'm bout to fix up my car and don't want to start until it is in tip top shape.

yea i'm doing the same right now... but yea it does it like once or twice a week wile idling... no matter wat the case... my tb was pretty dirty tho.. should be ok now, but only time will tell.