Engine stumbling after hard accelleration

[Vintageant]

Yesterday went on a 96 mile drive. On two occassions with hard accelleration through the gears, the engine experienced loss of power and faltering for several hundred yards, while I had my foot partially off the gas. Thereafter, with gentle accelleration up to and maintaining 3,500 rpm, the last 20 miles all was fine. Suspecting the Facet Rotary fuel pump 60300 installed 2019. And, yes, it's installed in the engine bay, not back by the tank! Thoughts?