ok everyone, 2001 GP GT 125,xxx miles on her... been in the family since she had 3 miles on her...

i recently took it off my moms hands for a DD since i have a TBSS as my toy... one thing i notice, while driving normally, the car shifts perffectly fine.. no issues, no slipping, nada.... but if i try to floor it, like say trying to merge onto a highway on the on ramp, or trying to pass someone on the street, the tranny starts slipping.. it will stay in the power band right up until the shift point, but when i goes to shift... vrrrrooooommmmmm it just sits and doesnt shift.. but this is only when trying to pass or "goose" it.. if i let off the gas once it slips, and the rpm's drop, it will shift into the next gear... again, while driving normally, keeping the rpm's between 3-4k, it will shift fine...

any ideas on what could be going on??