yup we had been there, but after changing to big tubing and DRILLED CLUNK we now even run our 91fx in our razzle fun flier, we hover and flat spin upside down and never had a dead stik.
yes we tune with a tach and run omega5% and use os a3 plugs.
and only the stock muffler.
GREAT ENGINE!! pic to show the fx and razzle and if you insist i will post a hover pic