RPM;s spikin....any ideas?

hey wasup every1....glad 2 see da site is finally up and runnin again after so long....Anyway....dis is my prob, every now and then (by this i mean it'll happen a few times in a day and then not happen 4 like a month) is dat no matter what gear i'm in or at what rpm, sometimes the rpm's will just drop suddenly a few thousand or so rpm and then jsut kick back up. Not drop the way it does when u put da car into neutral drop drastically as if u killed all da juice. A few times its even dropped 2 the point where the car has stalled out on me in da highway. And if i'm at a light and it just stalls, I can't seem 2 get the car started right away...It'll start up but then immediately shut right off. I've taken the car 2 my mech and he's tried hookin it up 2 da computer but u know da deal...it never happens when u take it 2 da shop....and since i don't get any codes....everything checks out "normal". We're both guessin its somethin in da distributor..maybe da coil but we don't wanna change a distributor and that not be it. Deos ANY1 have ANY clue what this coudl be.....my distibutor was changed about 2 years ago and was runnin perfect until this all started about a few months ago...There doesn't seem 2 be any pattern where it happens...its happened after a few minutes into my drive, after i've been drivin awhile, Highway, city, etc...Please help!!!!!