it will most depend on the exhaust manifold you allready own as the 18TZ is a rear exhaust and the 18CVR is a side exhaust .
After you will get more power with a TZ but all will depend on the gearing for the best speed.
I have the 18TZ in my RC10GT and to be honest i have to reduce the throttle % from my radio ,from 100% to 70% in order to not flip the truck over all the time at the end of the straight line , the speed is really stupid fast and the car becomes allmost uncontrollable ...