There is some type of break in proccess for new engines, but some people say to drive it how you would normally, some say to break it in slow, and others have their own technique for breaking it in (running certain gears for so long then swithching) Honestly I have no clue what the correct way to break an engine in, hell I don't even know what a re-manufactured engine is! Is it just a rebuilt one from someone else that blew a rod too?

I can't imagine that the elbow has anything to do with it, I would almost put my bet on you getting used to the rental car. Cars I believe FEEL faster since your all low to the ground and whatnot.

Anyway enough with my nonsense rambling, leave it to the gurus.