jba headers , slp exhaust ( loud mouth ), k&n air intake , how much hp do u guys think i will get from these mods ?

I'd say 35hp

Id say about 30 also, but I dont know how reliable the numbers are for the cold air intake, unless you get a ram air set up your better off getting a MAF, throttle body, or even a new manafold. The k&n intake is like 225 right.

The headers don't gain that much, as well as the cat back. The biggest gain you'll see from above is the K&N intake setup. I'd say 25rwhp at best but closer to 20.

I was figuring at the fly, but the headers give the most consistant increases, if the manufactures say 12-15 it'll most likely be in that range. Thats just my experience though.

I've been looking at a lot of dyno numbers lately. The shorty headers are not much better than the stock manifolds... maybe 5-10 HP gain. You need the long tube headers if you want more than that. Cat back exhaust is also only about 5-10. The cold air induction or K&N might be 10-15. After the mods, you should ideally get a dyno tune which should be good for another 10-15.

The JBAs are no better than stock, save your money. If you want to see gains, spend your money on longtubes and tuning. The cat-back is not worth more than 5 RWHP. The k&n will show gains initially, until the computer learns the a/f trims again, then you'll be lucky to show a true gain of 3 RWHP. With longtubes and tuning, you will most likely see 20+ RWHP, and the track times will show the improvement.