accel problems

I have a 91 LX 5.0 and it is completely bone stock. My father was the orig owner and I have had for a few months and drive it as my daily driver but, all of a sudden when i give it open throttle it hesitates after 4,000 rpm's. Like it is hidden the rev limiter. But not all the time... What should I change first? I was thinking spark plugs or fuel pump...
 
The TFI module mounted on the distributor is usually the culprit for a high speed miss on a warm engine. If the problem does not occur when the engine is cold, the TFI module is definitely suspect. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

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