I've got a discussion on proper shift points on my website. Give it a read; it'll help shed some light on the mystery. All the graphs in the world don't solve it all though. There's no replacement for test & tune to find out exactly what your car, and your driving style, likes best. Just follow the URL in my sig.
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Jeff Chambers
T/S #3
11.611 Seconds/116.7 MPH
Chambers Racing Team