1. You don't need larger fuel injectors until after you tune with the stock ones and they can't flow enough.

2. What does "valvetrain" mean? New cams plus valvesprings and retainers?

3. With aggressive cams you can benefit from raising your compression ratio, if you don't mind oopening up the motor.

4. If you're going to be running aggressive cams and a higher CR, you will see the most gains from a header with a 2.5" collector and a 2.5" catback exhaust. Nobody (well, excluding Hytech) makes a 2.5" bolt-on exhaust so you would have to have that made custom.

5. Ratther than drop the cash on the ITR transmission, I would just get a Quaife diff for your GSR transmission.