I have all three, but I do not run all of them at once. I use them as a tuning tool. The most I have used is two (front and center). Guys at the track say my car just explodes with foward bite when I hammer the trigger. Never get out of shape when I accelerate. Last weekends SIC race I just used the center. They do work. Are they totally needed. Absolutley NOT, but I do like them and the do work very well.