I have an 87 T/A 5.0 TPI and get a miss at idle after it has warmed up. Does not affect driveability and it isn't even there after 900 rpm just when sitting at idle. I changed the plugs, wires, coil, cap and rotor with no change to the situation. Any help would be appreciated.

 

I wonder if it could be an injector, just a guess. I dont think its an ignition problem - they get worse with rpm, and you covered that already. my .02 cents worth.

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91 B4C 305 TPI - SOON TO BE 383
TREMEC 5-SP, STOCK 1-BOLT REAREAND w/342 GEARS, K&N, AIRFOIL
EDELBROCK HEADERS, DUAL CAT TO HOMEMADE Y-PIPE & 3.5" SINGLE PIPE W/ FLOWMASTER, CRANK PULLEY, MSD, FUEL PRESS REG, COWL HOOD, WELD WHEELS
14.1@ 98MPH
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OTHER RIDE
67 CAMARO - STREET CAR, BIG BLOCK, PUMP GAS
350TH w/ATI 10", 12-BOLT w/373 GEARS
10.94@124.13 ON MOTOR - ET-STREETs w/MUFFLERS

 

Try a set of wire separators. A cheap set is like $2.99 at Autozone. Worth a shot.

 

Look for a vacuum leak