Its cool to tune over 700 horses on a street car from the drivers seat, timing , fuel and everything. I just needed more vacuum and changed to a one size smaller solid roller w/ a bigger lobe separation to get it, won`t lose very much at all. What if it does lose 10-12 h.p.? I seem to have plenty. I put about 25-30 miles on mine everytime I start it, even when it`s hi 90`s w/ hi humidity , that`s the way Ive been testing all the fan combinations.