Well at least when you don't hear it anymore you know what is wrong.

 

My Walboro pump is perfectly silent. Has been for 4 months.

 

what are the chances that extra volume being produjced by the 255 cannot be returned to the tank fast enouph and the pump is getting backed up, ant chance a larger fuel pressure regulator with say a satatic pressure setting and a rising rate setting would solve that problem.

 

Run on the bench without load the pump makes a pulsing sound due to the check valve at the outlet. This sound can be heard with the pump in the tank (e.g. when the system primes) at startup. When the pump is under load the pump's noise goes way up. The more pressure it is asked to deliver, the more noise.

Feel free to test the pump out of the tank, just don't run it very long as the fuel is the cooling medium for the pump (e.g. you will overheat the pump if your run it w/o something running through it.)

While you can get a neoprene sleeve for the pump I found that it wouldn't fit in the Evo's in tank assembly, and I really tried to stuff the pump with the sleeve up into the plastic tube. Any suggestions would be welcome.

At this point I don't have a Walbro in the car due to the noise, but there maybe little alternative in the future.