They decide to do an experiment- sex experiment
Here is all I remember.
He is working out in garage - she comes in and tells him about new experiment she wants to do with him.
They tie for best score at high school. They are asked to help ( chinese I think ) student who is working himself to death to become number 1 but too far behind them. They introduce him to girl ( from a sex store I think ).
Their parents knew they would marry someday but were shocked to find out how much sex ( bondage and etc ) they have experimented with.
It was a great story. Can you help me find it?