Coming from a motorsport background and the fact my uncle builds race engines(circuit) if you run an engine in gently and never get up it it will turn out to be a bit of a slug. On the other hand you don't go and thrash the crap out of it banging it off the limiter with 100km's on the clock. when running in a race engine, the method used is the same as I use on a road going car but over a slightly longer period. Apon on of my uncle's customers getting an engine built it gets run in the car first. Fast idle usually for about 30 mins to run cam in if cam is new. Otherwise it gets run in for a short period of time with some minor tuning and adjustments. From there it goes to the track where the owner does anywhere from an hour to two hours of track work not flat out but at varying speeds. Starting off keeping revs to half, short shifting for a good handful of laps then pitting for a check for leaks, timing, fuel adjustments etc. After that the driver goes out and increases rev shift point for another half hour or so until they physically feel the engine start to loosen up. At this point they then begin to use full throttle for short bursts on the straights obviously monitoring all guages etc. By the time 2 odd hours have passed they are lapping under full throttle but at the same time not pushing it to it's limits. From there it goes back on the trailer to the dyno where the fine tuning and set is completed and the car is now ready to race. This can be applied to driving your street car but you use the kilometres travelled as a guide. Break it in gently but varying your pace. Hitting lift is fine(I know I did!!) but not bouncing it off the limiter. I did about 500k's before i started to really open it up. With the way modern engines are built these days run in times are a lot shorter than say a holden red motor out of an EH. By the time 500km were on the clock I was hittng lift regulary as well as just driving normal and car feels fine. Ultimately if you could get on a race track and just do lap after lap increasing your pace as time goes it would probably be the best and easiest way to run a car in in a controlled environment. You would then feel when your car starts to loosen up and then start to push it that little bit harder. That's my way, if you like it then great if not then do it your way. Not twisting any body's arm here or say this way's right or wrong but merely offering my opinion! Cheers SILVABULLIT :D :D