1988 4.3 S15, feels like it's cutting out

I have an 88, S15, 4.3, Auto, 4x4, with 197,000 miles that's driving me crazy (crazier??)......It runs fine when cold. When it reaches operating temp and it's driven at around 40 to 50 mph, it feels like it's cutting out
electrically. It happens for a second and then will be ok for another minute or so, then it does it again.
It's not setting any codes. I've used WinALDL and see all the sensors responding as they should. Timing has been checked and it's fine. ESC is working because when I disconnect it I see the timing change........It has new injectors (Standard), plugs, wires, rotor, cap. My mechanic also changed the pickup in the distributor - since that was original. Also changed some vac lines that were dry-rotted.....All this, yet I'm still experiencing the problem. I'm stumped - and so is my mechanic.
I'd appreciate any help you can provide.
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Coil's bad. My '89 Blazer drove me crazy with a intermittent miss/power drop out. Mine would run fine unless climbing a hill or stomping on it. Will not set a code either. One night I got lucky and heard it arcing and then I saw the coil arcing. Remember it's intermittent and I just happened to be in the right spot with the hood up. If you look close at it you'll see the grey arc mark where it shorts from the coil to the laminated frame. Get a quality repl. coil , I cheaped out an put a AZ one it, lasted 2 weeks and same problem again until I put the NAPA coil then problem free after that.

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check your fuel pressure...9 to 14 psi with key on engine off..not within the specs replace pump..
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I should have said in the original posting that the fuel pump was changed about 40,000 miles ago and is within specs. Please excuse my error of omission.

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check your engine coolant temp sensor...
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I have a 88, K1500 with a 5.7L and it just started doing the something like that. It only cuts out after its warmed up, mostly after a short blast on the highway. It will miss and/or has no pwr at idle and at lower speeds. I can hear it ping badly and a few times it backfired into exhaust manifolds. It will do that for a minute and then run fine. It will not do it all the time, I can drive it 20 minutes, it will miss for a bit then run fine. Like you, no error codes. I don't think its a fuel pump problem, in that if the pump is actting up it it would miss longer and at all speeds, hot or cold, ( IMHO ). I am betting something with the ignition. I 'm just starting to look into it, and will let you know what (if) I find.
Mike

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It turned out to be a bad set of wires. Sprayed the wires with a misting bottle and it almost stalled. Replaced the wires and she's running like her old self.
Thanks to everyone who offered assistance.

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Iam having the same trouble , have you had any response? The only difference is that mine is a 1989, with about $2000.00 worth of new parts under the hood, plus ECM change and new fuel pump and tank.
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