You will obviously make power but not much.

Let me explain it this way. Assuming you have the Vortech SC already installed;

If you have a test pipe and exhaust, the header might add 10whp but w/o them, it might add only 5whp.

These numbers are just to show you what the difference will be. Don't take it as reference. It might be 15whp with exhaust and 7 with only header. My main point is that YES, it will add power but you won't see its potential without the exhaust and the testpipe

PS: Instead of the header, just put a testpipe, it'll add more power. The header on the S is already enough

 

If you just want more power and to keep your exhaust quiet......smaller pulley.

 

Agreed with everyone above. If you want more power get a smaller pulley. That's going to cost you about $120 for the pulley/belt and some tuning time on a dyno. You'll gain WAAAAAY more power than any other bolt-ons can manage on this car.

Back to your question: Because you are FI'd you should, theoretically, see greater gains from adding the header than you would if you were NA. Spoon makes a quality product. I suspect you will see some measurable gains but I don't think they will knock your socks off.

Good luck!

 

keep in mine that you will need injectors and ems too with the smaller pulley