need some advise on TPI not running well when warm

[CMACDONALD1]

Hey guys i have a 1968 chevrolet that has a tuned port in it that i did not install but when it gets warm it starts to stumble at about 2800 RPM and progressivly worse with RPM. my last trip out with it i drove it down the hwy and when it got up to tempurature it progressivly lost power untill it finally would not even run so i pulled over to the side of the road let it cool off and away i went again. My guess is that i have a fuel pump problem as it seems to be a bit noisy at times. any help or advise would be greatly appreciated. Thanks in advance.