Dang,,, where did I put those catalytic's anyway ?? Oh yes,,, in the storage building for safe keeping. Actually,,, @Larry Fine is about right. A small addition of extra oxygen at select times, can partially help burn hydrocarbon's in the cc's. Cheers,, CAt'"There is no significant performance advantage to be gained." But isn't it for catalyzer protection that they burst air inside the exhaust? I don't want those things to get stuck with carbon.