I had the same problem with mine. Done about 400 miles when I found it was on 1 cylinder. Took all the pistons out and found 3 out of 4 were cracked on the ring lands. Have sent mine off to the manufacturer to find out what has gone wrong. Has the piston got any signs of detonation on them?

16 PSi sounds a bit high if its on a standard setup. Low compression pistons might be the way to go.

Cheers
Dave