I have the full Belanger exhaust w/ smooth tubes and the Vec 3. My hp increase w/out the Vec 3 was to be approx 35, and w/ the Vec 3 my hp increase is 70 (according to Chuch "The Best" Tator). My car is naturally aspirated for now, like many of you, I am waiting on the Roe GEn 3 charger. The combo Vec 3 and exhaust system mods make for a very noticeable improvement in sound, acceleration, and gas mileage. The car just pulls and pulls, and in 3rd and 4th gear she really gets fast! I would not let just anyone install the Vec 3 as the programming is rather complicated. Also, it may need to be tuned and adjusted, each Viper is a little different so its not just a plug in. I read Sean Roes software booklet that comes w/ it, IT IS VERY COMPLICATED and should be handled by a trained professional.