Thanks guys for all your informative posts, very interesting reading and its the type of discussion i was hoping for.
I think you nailed it on the head CTR with your quip re 30 year old (engine) design, will it take the Chinese entering the GA market or a bigger version of the Rotax (due to the phenomenal growth in LSAs and their forthcoming increase in MTOW) to spur the big two into updating their technology?
As the price of fuel heads north at a substantial rate of Knots, more technologically advanced (and emission sensitive) engines are required, why this hasn't happened yet beggars belief!
I guess it all comes down to the old saying "if it ain't broke...don't fix it!"