I recall reading a bit about that installation. Apparently the great looking flush exhaust was a big mistake. I think it acted too much like a NACA inlet and produced a great deal of backpressure in the exhaust system causing the engine to overheat at higher power settings.
That seems like a pretty fundamental design error. Makes one wonder how well the rest of the installation was thought out though it looked like it had been done with a great deal of craftsmanship.
Work the bugs out and it would probably be a fun airshow ride.