I currently have two of the OD ss.21 engines and love them both. I have been able to keep up with and pass just about any other engine out there, but this mostly comes down to driving. you might want to take a look at the werks B5 I have heard great things about that engine as well. I went with the OD cause I have a OD z01b and just thought i would keep with the same company. Also check out the powerhouse modded novarossi engine i think its the bf.21 or something like that, that engine is great too. It seems that most of the engines coming out now in this price range have really great performance, not much of a need to spend $500 on an engine anymore unless you are competing at a really high level. hope this helps, feel free to ask questions.