Had the same problem, but I wasn't running an isolator and it was a stainless hose in the cab. 1st I was reading at the VP44 inlet - lots of noise. Moved it to the bottom of the stock fuel filter, better, but still intolerable. Finally, got a FASS and I read from the FASS pressure port. No more noise. Try moving the isolator (or where it reads pressure) as far away from the VP/engine as possible.