Vapour Lock Issue

Hi All,

I have been trying to sort vapour lock issues in my fuel system.
I currently have
1/2" supply and return line back to tank
Holley billet bypass regulator
Claysmith mechanical fuel pump
Tank venting has checked out fine

The issue only occurs when I sit at 60mph on the highway, it just coughs and dies.
I though the bypass reg and return line had fixed it but not so....although it has helped compared to the deadhead reg.

What else can I do to rectify the problem?
The fuel lines and carby get warm but not overly hot to touch.
Thanks.