What would you suggest?
T04R <<< upto 620/650 hp
T04Z <<< 650 to 800 (spec dependant)
Both have low lag (for the turbo size)
With a well spec'd housing (both) trim and wheel spec the T04R could be a great turbo, on the road and track (good engine spec also needed, C/R, cam choice (and dialled in well), and the right head work.