The car uses a mass air system. As long as you aren't overrunning the maf with too much air or maxxing your injectors to supply the extra fuel then you don't desperately need tuning. Once you change injectors though, a tuning method is required. The computer needs to know how much fuel the new injectors are putting out with x amount of open time.

You have a few options:

1) SAFC: Cheapest solution(unless you already have an Eprom ecu, in which case see one of the following alternatives... which all require a socketed Eprom ECU)

2) Have someone burn a chip for you with the new injector size. If you don't have a chip burner yourself then this can be a pain to make other tuning changes.

3) DSM link: Nice easy to use interface, but expensive.

4) Ostrich emulator + Tunerpro RT: This is the best alternative so far. As long as you can learn Tunerpro, you have full control of your ecu.

5) Ostrich emulator + DSMap: Ditch your MAF and get a 3 bar gm map sensor and IAT. Install DSMap. Enjoy almost all the functionality of an AEM EMS for less than an SAFC. Harder to tune though. Need to have a good grasp on tuning with Volumetric Efficiency.