Something is not right with this conversation. The equation of Power relative to torque is P=2PiNT/60000 where power is P, Torque in Nm, N = rpm, Pi=3.1416. If you maintain the Power and change the rpm, the Torque is affected. I dont see how you can go from 31" to 33", be happy with the driveability and not realise the issue is the impact on the avail torque as you are probably sitting at a different spot on the torque curve. Swapping diff ratios is only going to land you back where you started - I think, as others have suggested, you look at the power component of the equation to get better driveability as the torque curve will change to compensate.