Quote Originally Posted by chevynut View Post
Is this a new problem, and did the car run fine at 90+ MPH before?

What "return line" are you referring to? Are you running a regulator? Holley says you don't need a regulator with that pump. Also, you said you have a 3/8" line "from the pickup"....is the pickup itself a 3/8" one inside the tank?

I had a 55 Chevy with a '67 Corvette 390 HP 427 in it and it would starve for fuel at high RPM....similar to what you're describing. I used the stock mechanical fuel pump with the stock 5/16" line and I'm pretty sure the line was the problem. It needs to be clear all the way to the pump with no restrictions. Make sure you don't have any restrictive fittings in the lines.
I believe it is a new problem. But it did happen on a warm day with winter gas, just not as bad as before. The pickup is 3/8. I don't know what it is here, no one else in other area's has fuel that boils so easy.