Originally Posted by NSFW
The first guy who wanted to adjust the fuel pump duty cycle was actually doing it for noise reduction, but the other way around. He said his pump was very noisy when running at low speed. At 100% it runs quieter. Go figure.
Tons of Impreza people are running Walbro 255s off the stock ECU, I'd be very surprised if that setup was really problematic.
My friend's setup with dual Walbros sounds like a jet about to take off when only the ignition is on and the pumps running at 100%
For people running E85, they might be teetering on the edge of not having enough fuel pressure with a single pump if they are running higher boost levels. That's why we went with a dual setup pulling power off the battery. The car has a TD06 20G and Bosch 1000cc injectors with E85. My friend used a fancy spread sheet accounting for actual flow rate, IDC, and fuel pressure to realize a single Walbro wouldn't be enough.