Using bigger injectors than needed requires less fuel pressure in order to run properly, but lowering the pressure screws up the spray pattern, and the results still suck.
Your engine sounds nice, but I don't see any reason why you would need anything larger than 19 pound injectors. Injectors do become dirty, and that affects the way they work, so cleaning or replacing them would be your best bet, IMO. Actually, you can get a set of 19's for about the same price it would cost to have them professionally cleaned (don't buy into the $39.95 gas station special), so if it were me, I would just get a new set of 19's.
But that's just me.
Take care,
~Chris