The c11 is better than flash and 35plus21 ,I'm using rb 2018pipe or rb 2092 it perform close to the nova keep on ,best is to use o'donnell 99plug or os RP7 ,infect the new cxr is the same as the c11 only different is the sleeve got 2 more tiny port below the exhaust port for more cooling but it makes no different to me , heat sink different only the wording, i have both cxr n c11 love both of them check it out at amainhobby they are offering rb now with c11 at usd $399 at this price u can out run most others race engine. don't get the cx it a waste of time as the crankshalf is not balance, not hard coated on crank pin no silicon paste plus no ceramic bearing not worth the price u paying for