Chased carb/pumps issues. Told my engine builder my "thoughts", he told me , "how do you KNOW it's the pump, you have a fuel pressure gauge?" Lesson learned. Best way to narrow your issues with fuel delivery is install a fuel pressure gauge. You can install a permanent electric one, or run a rubber hose type temp one, but until you can verify FP thru all ranges, you are only guessing...my experienced 2₵
