I really like the CPI Pipe [link]http://www.largescalerc.com/cpitunedpipeforbaja5b5t.aspx[/link], it's well protected and really wakes up the stock 26cc engine . I use one on my 5T and it gives me plenty of power, here is a video of me running the CPI pipe with the stock engine.
http://www.youtube.com/watch?v=WcOPCDb3Xzk