HDDP.... That Kleeman guy is full of crap and obviously has no clue what he's talking about! It's a very noticable improvement. Especially in mid and high end torque. My 0 - 60 times went from 6.4 seconds to 5.7 seconds. That's with nothing more than K&N filters and Upsolute chip..... If that guy is typical of the folks at Kleeman I wouldn't let them work on my lawnmower. He doesn't know is butt from a spark plug.:lol: