NORM - Not sure how much flow the pump in my home-made parts washer is, but it's the same pump Northern Tool puts in their parts washers. I sometimes wish it had a little more flow, but it's just right for almost everything. Too much flow/pressure would cause splashing and make a mess.
Some people have good luck with the water soluble cleaning solvents, but then I've heard people complain about them growing bacteria and smelling bad, or freezing.
I built my parts washer about 15-16 yrs ago with the old worn-out 20 gal pressure tank from my well, turned upside-down. The bottom was rusty, the top was like new. I made a basin about 18" x 36" x 6" deep, put a big drain in the basin, use the flow-through parts washing brush, and for fussy things, I use a 1/4" in-line gas filter to filter out dirt from the cleaning solvent. And the pump was the replacement pump from Northern, a submersable pump specifically made for parts washers.
I use a gallon can of GUNK degreaser and 4-5 gal of kerosene for solvent. But with the current price of kero I might try something else for solvent next time.