My 99 mustang GT has a trouble code that keeps reappearing.?

I just installed an after market throttle body on my 1999 mustang gt. I did the install properly and had it checked over by my mechanic. I realized that i was now getting an error code that i read as an issue with the Throttle Position Sensor and to much throttle slack. Throttle response being now different but improved i cleared the error code with my handheld tuner, yet it keeps appearing. I would like to know how to make it go away and stay away so my check engine light will only come on if there happens to be a real problem.