Do you lose mph with the E.T. Genie ? I know I did . 2 to 3 . I actually had to modify my Moroso stop to make the bolt for the linkage stop longer. Still works well until I reach a certain point on the adjustment . One thing we found while running my current engine on the dyno was that using my bolt system really didn't hurt my air / fuel readings , we have heard about some stop type systems causing havoc with the readings causing weird things to happen in the intake manifold. Another brand x engine was dynoed with an E.T. Genie and it too showed no ill effects .