2005 Mustang StreetFighter Torque Converter need help part2

hi ppl

just got my 2005 Mustang StreetFighter Torque Converter put in at my garage. done all the tunes what was needed from brentspeed.
went to take it for a drive pulls lovely in 1st and 2nd BUT it dosent want to change to 3rd it keeps hitting the rev limiter. then after the over drive light comes on starts flashing on and off. so we took it back to the garage they thought it mite not have enough fluid in the transmission. they put some more fluid in took for drive agen same things happon ?

But when i drive slowly all gears work ok its only when i pull my foot to the floor. i tryed it in stock setting but still dose the same thing it drives ok when im driving slow but its like the transmission jumps somtimes when its in gear. but when i put my foot to the floor 1st and 2nd ok but hits the rev limiter in 3rd and after over drive light comes on and starts flashing on and off agen

so it not? the tune it most be somthing with the converter then ???

any ideas

thanks agen