im not 100 % sure if the exaust are the same on to .16 and the .18 engines but i put a tuned header and also took the baffle out of my muffler and got a pretty noticeable power increase[link]http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=001175464&I=LXBTB5&P=K[/link]
here is the link for the header