01 Grand Prix GT 3.8L already added K & N Air Filter, (hoping for more power), Thinking of adding headers.Is it worth $900-1100 dollars to add headers to my car? I like sleepers. dregen63@gmail.com

I got a 2001 Grand Prix GT, 3.8L with 96K. I recently added a K & N air filter to try & get a little more HP. I definately got a little more, but now I'm thinking of adding headers, how much more HP can I get? Would it be worth the cost? Plus, I don't want both headers to connect to a  "Y"  pipe & then run 1 pipe back to the mufflers, then split to 2 exhaust pipes.  I know I need more air flow in for more power, but in order to achieve that, I need to have good air flow out. That's where the headers come into play.  How much more HP can I get with headers? I don't wanna to race it, (only if I have the opportunity to, wink, wink), but I don't want to spend a fortune to do that. Anyone out there got any ideas? Me personnally, I like having the sleeper race car, low profile, so if the time comes, a few bucks hopefully will come with it.    dregen63@gmail.com