I've seen the RPM products but I'm not familiar with Integy. My concern is with alignment, camber and toe-in. (Anything that might keep the truck from going perfectly straight.)
I run a street truck. I'm still running the HPI Nitro MT on a parking lot oval. Using an OS CVR with a 2 speed, it goes pretty good, but I'm at the limit of my limited driving skills and want to get things as tricked out as possible. (By the way, you and some others offered some advice about diff shafts a couple of months ago. I've not had any problems since I went to the longer nitro rush diff shafts.
Where can I find some information about the Integy tuning kit??