Auto Racing: 2004 V6 Mustang, cold air induction, cold air induction kit

Question
I just installed the BBK cold air induction kit into my 2004 V6 mustang and it is great.  Supposedly it adds 12hp and it sounds and feels good.  Thank you for your past help about the intake.  Anyways, I am now looking to add another part that is in the $150 to $400 price range that will add a decent amount of hp.   As of now I have not been able to locate such a part, so if you have any idea of what I could possibly do that would be great.  I looked into getting eibach springs for my car but the springs are $250 and the installation is like $450 which seems a little over priced to me and I can't afford that.  I also found a good Ford Racing ring and pinion set for $180 but the installation is again outragous at $500 which of course I can't afford.   Thank you so much for your help, you are the only expert that has truly been any help.

Answer
Bobby-

 Actually, my first suggestion would have been a ring and pinion set which won't add any horsepower, but will be a serious kick in the pants.  If a shop is asking $500 just for the install, look elsewhere.  I've never charged more than $400 for an install...that's if I get the ring and pinion (and you can find sets cheaper than $180...just because it's Ford Racing doesn't mean it's the best and certainly it isn't the cheapest).  Also...$450 for a spring install?  I don't know where you're going to get these estimates, but they're insane to me.  I suppose if we exclude those two, you could look into a set of underdrive pulleys.  A set of MAC pulleys gained 12hp on a 4.6L in a magazine test a while back and I've seen pretty similar gains.  On a V6 I'd imagine you'd see a bit less, but they're not expensive and they add power.  Lastly, exhaust.  It's important to do exhaust right on a V6.  The best way is to pick your muffler brand and then install a resonator along with it.  Without a resonator the sound can come out pretty bad.  Hope this helps.

Steve