Hi Bob!
We just made a video series about our 165hp Edge Performance engine conversion from a 914 Turbo.
We address all the reliability related questions within the videos as well as how they are built (part 2). And compare it to the Rotax 915is.
But a short answer here would be that more than 250 such engines have been built since 2006 and none has failed. Some has more than 1200-1500 hours. And the conversion has been extensively tested to well above 200hp. So they have a perfectly good track record!
Here's a link to the 1st video:
https://youtu.be/f0n0Z0YrRH0