I'm having exactly the same problem your having, for the last 2 weeks I'd be driving say 55 mph and all the sudden the engine isn't running.. I'd coast for about 5 seconds and then the engine IS running again and power comes back. I have been trying to figure it out in my off time but im working tons so its hard.
Today I got my slap in the face, I was crusing down the street got to a light at a VERY busy intersection, it died but i was almost last in line so I motioned to go around me. I got it started and it drove 30 feet and parked it for 10 minutes although I knew already at this point it had nothing to do with heat.
It starts up very easily so I think I'm alright, I pull out of the place and pass 5 cops >_> get to the next intersection where I need to make a left. Dead. It starts runs for 1 second, dies. Again I'm at another gigantic intersection so I push it through the red lighted intersection (thank god I'm in my orange construction worker gear still). I immediately go for the fuel pump relay, I remove it, clean it, the harness wires look iffy so I cram them in a bit.
I crank the engine for 25 continuous seconds and then boom for no reason at all it starts, and dies. I crank it again and it starts ok but its missing BADLY.
I couldn't keep it running with anything less than 1500 rpms and it sounded like a freaking harley bike. I kept at it for 2 minutes and the idle smoothed out with very occational jumps here and there.
I could feel it was 'off' so I powerbraked it all the way home keeping it at about 1100 rpms (this by the way makes it VERY hard to stop
The fuel pump seems to be working whenever I ignition on though.. I am having the worst luck figuring this one out.
Things I've replaced trying to solve this in the last few months
Ignition module on distributor
-swapped back and forth my msd 6al with no luck-
I'm thinking it might be the computer but I was hoping you guys might know something more obvious
Always true since I got the car are:
Runs super rich
Idle never very smooth
No engine codes
in the aftermarket segment its an msd coil and 6al ignition w/ shorty headers and no knock sensor.. (dont ask)
computer seemed to be already non stock and there's a hypertech chip i added...
I'd appreciate any thoughts, also it might help with dak's iroc cause these computer controlled monsters are too complex
Edit: Oh I forgot to mention, the problem started 6 months ago as seveer hesitation on bumps and other bad road imperfections while at WOT only.. wtf eh?