my 2001 F250 7.3. It only has 88000 miles on it. It's up on 40's. It's got upgraded turbo, 4 inch exhaust from downpipe back, and k and n intake. just had the tranny rebuilt... Now the truck seems unhappy... When I step on the accelerator pedal to speed up, the truck takes a long time to down shift. I have to really push the pedal almost all the way down before it will down shift and when it does, and the rpm's climb, but it doesn't seem to accelerate, like something is slipping. Especially on the freeway or uphill grades. When the truck won't down shift and I step on the pedal, it causes the truck to shake. When the down shift finally happens the rpm's climb but I don't seem to go any faster or gain any speed. The truck also upshifts too early around 35 to 45 mph and this causes the truck to shake also. any suggestions would be greatly appreciated.. Don't know if it's a boost problem or the torque converter...HELPPPPP..