Dynoguy --
I do not use Foaming in my Shop, but I do know about pressure washers..
Gas or electric the amount of pressure, (psi) pounds per square inc, and gpm (gallons per minute) is all you need to know.. Well, and of course, how to use the machine..
If you know the pressure of the machines and gpm, and can get them as close as possible, if this is where you want to keep and use the machine, then that is all you need to do, match both numbers as close as possible..
I don`t know of many electric pressure washers that go much beyond 1500-1600 psi, while gas powered ones can go way past that number and of course be more dangerous to use for cleaning, if not experienced, etc..
The gallons per minute (gpm) number means just that - how many gallons of water per minute is going to flow through that orifice tip at the pressure (psi) number...
Of course, the more gpm the more quickly, efficiently, you can go, but again, at higher pressures, you have to be really careful and never hold anything really powerful up really close to a painted surface - ANY painted surface..
We can talk about the tips on the end of the pressure washer wand if you want to..
Dan F