Depends how nuts you want to go, the bikirom daughterboard (running version 3 software) is more than good enough in the R34, especially for the price. You've got full access via USB to most of the maps you'd want to frig with. The only thing V3 is missing is real-time upload, but that's been sorted with V4 anyway...so bit of a moot point.
So easy to tune now it's sickening, shame it was like this out of the box 2 years ago, took time to develop I suppose.