Check out some of my testing I did today here http://www.frybrid.com/forum/showthread.php?t=1169

Did a flow test on the Cummins electric supply pump verses the GM unit. I was quite surprised.

Used a flow meter calibrated in
PPH Liquid G. 0.81175 Visc. @ 95 degrees. using VISCOR test fluid (about the same as diesel)

Cummins
PSI-Flow PPH
9- 260
10 -242
11- 217
12 -184
13 -146
14 -115
15 -92

GM
4 -115
5 -94
6 -88


You'll have to convert that to gallons I guess. I guess you can see the GM unit is very lame. No wonder the unit loses pressure at speed. The flow meter is used in the calibration of Cummins PT type pumps on Cummins big engines.

Both tests made with good used units. From what I see the Cummins unit should be able to maintain 13 PSI on the GM at W.O.T.