i have not seen much if any difference in hp from a new engine with few miles on it, to a engine dynoed with several thousand miles. leak down is were its at, we dyno a race engine until the leak down comes into specs, usually this only takes 2-3 hard pulls. i have seen engines go from 20 percent leakdown to 4 percent in 3 dyno passes. depending on how you drive and what oils you use your ring seat time will vary. anyway you want to put it the new apex is 10+ more hp than the rx-1. the throttle response is awesome, and they handle like a dream. jeff