The time tested and proven best way to break in an engine is to:
1. don't let it get too hot.
2. use a higher oil to gas ratio for the 1st 5 tanks of gas.
3. don't run it too slow all the time.
The best thing you can do is run easy until the engine is warmed up. Then open the throttle until it gets up to near top speed, then back off and let it cool down. About 20 or 30 seconds of full throttle is good. Don't do any long runs without shutting it down to cool off. The heating up and cooling down often speeds up the break in.
As time goes by, gradually increase the time you run it fast, and by the time you have burned 3 tanks of fuel the engine should be good for the long runs.
Before you go very far, check the oil in your transmission. My Avanti came to me with about 2 ounces of oil in it...Ken D