At the track last night it would level off and loose power?

Thanks for all the replies it is sounding fuel related, I built the engine and car but I know nothing about tuning and such.

To answer your questions It was the cars first time out.

Ran 150 degrees the 30 mile drive over and 180 degrees on the track.

Timing is 15 degrees and all in at 2500 35-40 degrees. Mancini elotronic distributor with built in performance curve, hei coil.

Exhaust is 2.5" with dynomax straight thru mufflers

Manual fuel pump 5/16 line and 5psi fuel pressure , Eddie performer 750 carb.
Run times were;

R/t. 1/8. 1/4
.159. 9.75@70mph. 89.42 mph
.574. 9.8@69mph. 87.58
.869 9.9@ 64. 80.22 mph