Well, I noticed longer life and better performance from my dirt bikes when broken in in the mountains than when broken in on the flatlands. I applied the variable load concept with high throttle at low, then increasing rpm gradually when I started racing modified outboards, and had some very fast and durable engines. I ran a different exhaust than everyone else (chambers instead of megaphones) but I think my edge in power was as much from the break-in procedure as anything else.