Basicly dajo hit it on the head.
T5's-good all around pipe, respond good to mods but still run awesome with a stock motor.
CPI'S-not an all around pipe. mostly made for sand dunes and drag strips. Responds awesomely to mods (carbs/porting/reeds) pull HARD in the high RPM range
keep your t5's until you go to a 4mill+ stroker, insane porting, and alcohol
P.S. if you decide to sell your t5's hit me up