first time

[Rocket 99GT]

Hey guys, first time in this chat. I ordered a
stage G-Track stage 1 and stage 2 steeda suspension kit, a march ram air system (any of you guys know if this ram air system works), I also had the dealership change the gear ratio to 3:73 and got 4 new Michelin Pilot XGT-Z 245/55R16 (present from my sweetie for Christmas).
I am just starting (is a very expensive hobby), I want to change a lot of things but I don't know where to start. How effective is a computer chip, should I buy "H" pipes and a flow master muffler or should I upgrade the engine with bigger injectors (any idea what the stock size of injector is in the 99gt). If I start from the engine where do you guys take your car to have all this work done. I know that if you change the injector you have to recalibrate the MAS sensor. I called my dealership but they refuse to do this work.
Last question any of you have installed a WMS calibrated Pro-M87mm MAF, I was reading about and they claim 25 extra horsepower.
Please welcome me by answering the questions, after all I am just starting.