I went from the stock size of I believe one at 65 lbs per hr and the other at 68 lbs per hr to 80 lbs per hr for both. I did not change my fuel pressure and left it at 16psi. As I understand it every two PSI increase flows about 1 lb per hr more so I was pushing a bit more fuel than the stock flow rates with my PSI setting. The main reason for doing so was it was going lean in the upper RPM @WOT. The car reacted very well and according to my A/f ratio gauge has good/normal A/F's at idle and part throttle and swings 12.0-12.8 @WOT. I did upgrade to a heated 3 wire O2 sensor which helps I believe. I can feel the difference pulls much harder at WOT and feels better everywhere else actually. The old injectors were basically new as I replaced them not too long ago and run a 85 TPI pump. I'd say if your chasing a fueling issue rather than messing around with fuel pressure too much and cranking it up, up size the injectors and run a closer to stock fuel pressure this seems like it would be easier on the fuel pressure regulator and gives more upside fueling potential.