ORIGINAL: poor judgement
if you would really like to go crazy get the os 18 tm rear exauat 1.6 bhp compared to the cvr side exaust 1.35 bhp.
i seem to remember seeing an article that gave dyno readings for these os engines. iirc the cv-r was measured at 1.6hp and the tm came out a little over 2hp. i know 2hp from an 18? sounds a bit iffy... but we all know os are conservative with their figures. i think 20-25% fuel was used in the test. if i come across it again i will post it here.
as for whether u should get the os to replace the sirio.... i would, purely for the midrange power of the os, top hp figures dont tell the full story, its torque and width of the power band that are important.... so get the os.
edit: well sticking "os 18 dyno" into google gets this up
http://www.rccaraction.com/rc/storie...es/%22&sgid=20 ok its the tz not the tm....but there u go
U think i would be able to trade my sirio for the os 18 tz? lol