Just finished installing my Steeda UDP's a lil while ago. Install was easy and the how to write up on here worked perfect. No problems whatsoever and def. recommend people to do the install themselves. Save your money and dont pay someone else to do it. As far as performance. I cant say how many hp but i can def feel the difference as well as visually see and feel how much quicker the car revs. Just thought i'd throw this post out there for anyone thinking of doing this. Well worth the money