A good rule is a compression reading. All the mods under the sun will not yield maximum results if the heart of the machine is lacking a healthy motor. Another good way to tell how the car is doing is your TQ output. Anything over 400rwtq around 15psi is kicking ass. The rwhp can be adjust with afc/afr, timing. The light weight driveline parts will help as well. The flywheel will free up Hp and the one piece driveline with be a direct link from the transmission to the rear diff. Plus both items free up around 56lbs of weight.