Hi, i have just put in a Type R Gearbox with 50k miles on it and when i drive down the road the car pulls to the left when accelerating and then when you lift off the car pulls to the right???

Could it be the diff or is it just tracking/alignment?? I did not mess with the track rod ends when installing gearbox just took them off the hub. I thought alignment would be ok.

any help would be appreciated