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

Update; I checked plugs and it was a little lean but not bad. Replaced everything from the line from the tank on. Replaced mech fuel pump with a edelbrock 110 gph pump, removed pressure gauge and regulator and plumed from pump to carb with 3/8" line. Seems to be much better sound at road speed,response etc but the track is now closed for the winter up here. Thank you gentleman for all your advice and time. Trying to schedule Dyno time in the next week or two and that should answer any questions.