i have ruled out the ignition relays cause changed them... car revs and drives perfectly as long as its under 3000rpm no problems what so ever... i have a first gen 13B with the racing beat holly carb set up...... It sounds like the trailing plugs cut off of something after 3500 i dont understand please help thank you

 

Start simple. Ohm out your spark plug wires. Then check your igniter etc.

 

explain