hey buddy,
wel first up a set of s15 injectors will make things a bit better but will require an ecu tune.
the flow rate of the standard U13 injectors are 370cc, the S15 injectors are 440cc so give a little more room for power.
secondly, a walbro 255l/h (550hp) fuel pump will make a very good improvement over standard. these pumps are smaller in size than the standard pump so fit straight into the original position. i have a walbro for a mustang in my car, but pretty much all of them will fit no probs, the in tank pumps anyways.
if you do get some new injectors my advice would be getting a set that will do what you want them to do in the long run. ie: if you are looking to set the boost alot higher than standard like say 15-20psi then go with at least 550cc injectors, otherwise you will run out of flow again. i am not saying that you are going to do this straight away but it is a pain to change them and waste money again.....