Are these things dependent on good voltage to run quietly? I had a Holly "Red pump" in my car...sounded like an idling chain saw. Switched to a Carter P40-70 that was supposed to be near silent. Stated out fairly quiet but by no means near silent. After running for an hour or so, its loud now too. Both pumps were rubber mounted. The only thing I could think of was maybe my wiring has too much resistance? I'm running a '54 Pontiac that's been converted to 12V.