i agree totally, the r154 is much smoother and w58 is even smoother again but your restricted from the torque the tt engine has,r154 is not a bad option ive been there....also tt lsd is much better suited if you dont wanna mess with it that much, all you need is lsd and half shafts, and with that add a rear sub frame mount and use a spliced tt prop(diff end) and w58/r154 on the gearbox end,ive got one spare if you ever go this route, as previous post says the r154 isnt cheap cos youll also need to modify shifter poss £150 if you send it in,and buy a 1jz bell housing-£300 from mr T,easiest way is just buy a 1jz gearbox that way no bell housing is required but there probably just as rare as the v160!
good luck m8!