I seem to recall an request for an exception for them, which was turned down. The replacement part rule stipulates no material change, so I feel they are illegal.

Reason for the rejection was that if allowed, all such requests would need to be allowed, such as Golf owners wanting to upgrade hubs and so on.
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Yeah, I have no issue with not allowing them. Unless you shim the hell out of the pump spring there is no reason there should be a huge problem with them.