I agree that this thread is based on club rules. But, it is my position to keep club rules as close as possible you our pro rules, so that there is an easy crossover.
It just seems to me that if the club simply manadated certain engines to be eligible and the pro series established weight penalties on new engines once they are proven to be superior, that this whole restrictor BS can be put to bed.
SIR single inlet restrictors will not work in FB as many engines still use the stock airbox (which has dual inlets). SIR restrictors can only be policed by stall tacktics. None of the airboxes which I have seen are that complex as to not have any blow by.
It has to be a situation where the club and pro series work together and have certain leeways in how they operate. It's best for the future of the class.
Once the evolution has evolved and there is a new engine established. the club than then choose how and weather to let them in.