Yeah Hesky, I agree. The O.S. .18 cv-r is going for right around a 100.00 dollars. Much more bang for your buck. A good all around engine, that stays tuned and lasts a long time if maintained properly. I am putting that engine into HPI's MT Racer, along with the cvec. I'll have all I can do to keep it on the ground.
Even with the stock exhaust it will be a much more noticable difference. I just don't think the cvec can pull any more out of the stock motor.