Following suggested maintenance, using a larger prefilter, and if connected to any tubing, keeping the runs as short and straight as possible with a size bigger diameter tubing.... will all maximise the powerhead output.
Overdriving the powerhead with ramped up current is going to cause premature wear and risk electrical shock to you and the fish. Mods to the housing do greatly ramp up water flow, but create a new set of issues, including wear and problems securing the powerhead so it does not break free and destroy the tank. The housing was extended, and had Venturi effect openings, and the rotor was modified with a larger propeller-like rotor on the end that fit into the new housing.
Someone demonstrated theirs at a fish club meeting last year, and it created amazing water current, more than you could get with a trolling motor for bass fishing.
They were discussed on Reef Central last year, but have not seen any recent developments.
A kit might be easier than replicating each needed part from model boat parts and plastic pipe fittings. I'm sure a lot of powerheads were tested to oblivion with different designs before coming up with the final mod kit being marketed.