Hi Skip, don't take this as criticism, but you may be looking in the wrong area.
It seems that your fuel delivery system may have a lot of restriction (lines, connectors, pumps etc), which is limiting pressure and flow.
As an example, the Sportstar POH actually says the boost pump is on only for start up and emergencies. It's off at all other stages of flight, including take off and landings.
The boost pump is actually an optional extra for the Sportstar, ie - the fuel system will work just fine relying on the Rotax pump alone.
I'm not advocating deleting the boost pump, having the boost pump there is more than nice, redundancy in an aircraft critical system is a good thing to have. But I don't think your fuel system should rely on it to give satisfactory performance.