You don't really NEED 21lb injectors, but you can still use em (make sure your car is tuned for them). Don't get what you mean by y-pipe resonator...You can optimize your y-pipe, that'll help. A K&N I wouldn't say necessarily does much, give your car a better sound, maybe...MAYBE a 1 HP. lol. uhm, and I would suggest a local place to get your car dyno-tuned over a mail order chip. Dyno-tune will be perfect for your app, but a mail order chip wont be, although if you can't afford the dyno time, ADC would be the way to go.
With all this done, you should expect some decent gains...nothing that is going to throw ya back in the seat and make a HUGE Noticable dif tho...
