surge between 3rd and 4th gear?, HELP

I had this surge between 3rd and 4th gear when accelerating at highway speeds, about 45-50mph. i took it in to the dealer, they had it for 3 days, replaced the torque converter, replaced the valve body, replaced all the seals, flushed the tranny and put it back together, and it still has a noticeable surge, it is better but defientely not right. i might take off my gen II and magnaflow exhaust and take it back in, but before i do does anybody have an idea? i cant go another few days without a vehicle. Thanks