Good morning all. I have a somewhat minor problem that I’ve been unable to solve on the MGB. When running along at 65+, in 4th or 4th OD for 10 minutes or so, the engine sounds like it’s being starved for fuel. It’s a performance build using a later block after I blew up my original 1970 engine...9.5:1, VP12 cam, Abarth exhaust system, big valves, etc. I’ve removed the vented gas cap, checked the fuel filters and verified that the fuel pump is working well. I have a new gas tank and rubber lines, but the original hard fuel lines. The carbs have been rebuilt and adjusted and it runs just a touch rich, but not bad and drivability is excellent. If I let off the gas for about 5-10 seconds it cures itself until I run another 10 minutes at speed. This has been going on for a couple of years, but hasn't bothered me enough to seek help...I thought I could figure it out. Now I need your expert trouble shooting to guide me!