Because of the demands for an absolutely consistent engine, I don't consider anything without 1) being designed for the rigors of pattern, and 2) a regulated pump, to be suitable for competition. If the Irvine can prove to handle the loads placed on it by the pipe for more than one season without a major rebuild (bearing replacement does not constitute a major rebuild) and you add a pump to it, then I'd consider it. Personally, I rather have an older YS 1.20. They put out a lot of power and very reliable.

Just my .02

John