There are many other significant factors that would effect your car's horsepower and fuel consumption besides having 1st size over bore pistons. The over bore size difference is essentially insignificant. More significant things might be turbo boost setting, fuel mixture settings, tire inflation level, lubrication, and so on.
If I were you I would wait for some period of time before cutting off the engine. But this depends on what kind of driving you were doing just before shutting down. If you just came off the interstate to a rest stop, I'd idle much longer than 15 seconds. If you live in a 25 mph residential neighborhood and have to go that speed for five minutes or longer to get home, then that's almost the same as idling as far as the turbo is concerned.
500 miles sounds good for the first oil change after rebuild.
If I were breaking in a newly rebuilt engine, I certainly would not be trying to find out how much power it had over my other cars or running it up to 75 mph.
Here are some break-in tips from one manufacturer:
- Keep your speed at 55 mph or less for the first 500 miles.
- Don't drive at any one speed - fast or slow - for the first 500 miles.
- Don't make full throttle starts.
- Avoid making hard stops for the first 200 miles or so. (This does not apply to you since its a brake issue.)
- Don't tow a trailer during break-in. (Guess that doesn't apply to you either.)
So, in a phrase - "Take it easy"
Your car has had some serious heart surgury. Don't start recuperation with wind sprints or a marathon.
Ken300D