Hi All, I don't know if this has been posted already but the L & N model inlet rubbers, part No 16211-KAZ-000, have a 27mm diameter opening whereas the later models, part No 16211-KAZ-780, have a 24mm opening. I know this because I bought both parts so I could find out what the difference is and to keep in case we want to make these later when they become extinct. So I think we can assume that this is a very large part of the restriction to lower the power of the later models. Cheers Blair