Onetrack,
While I can't/won't say much about Foxcon, I will take exception to your generalized comments about Subaru engines being " just not up to it". How do I know? - I have worked on and driven Subarus as our family cars since the early 1980's. I also have been flying my 19- aircraft behind a Subaru EA81 for 830 hours over the last 15 years. I elected to power my aircraft with the Subaru rather than Rotax for 2 main reasons:- the early gyro musterers used EA81 engines both as direct drive and with Rotax or Hirth gearbox reduction drives or various toothed belt redrives. They literally thrashed those engines unmercifully, with very few failures. I have rebuilt engines for these gyros. The other reason is that my entire firewall forward installation at the time cost under $5,000, and servicing and maintenance costs are negligible compared to the Rotax. And I chose to use the belt reduction drive made for Foxcon, which if set up correctly and maintained according to schedule has been very reliable. My only penalty for this choice is a 20Kg weight penalty over the Rotax published weights, every item of installation accounted for and weighed in order to calculate W&B for engine mount design.
BUT, like any engineering work, the quality of the finished product depends on the quality of the workmanship and of the components used. I did my own conversion of my EA81 after inspecting "commercial" conversions including that done by Foxcon on the Terrier. I did it my way, and have been rewarded by the reliability to date. No oil leaks or excessive consumption, no valve issues, no deficient valve springs, no head gasket leaks. It is the much later EJ25 engines that suffered head gasket issues, usually after overheating from coolant loss due to poor maintenance.
I agree with you that the Terrier performance figures are not substantiated - I wouldn't dare to claim 100 HP AND reliability from an EA81 being run at the revs necessary to achieve that output. I estimate about 90 HP maximum and I cruise at 4,200 rpm maximum, closely approximating the engine revs of a 1980's Subaru 4-speed at 110 K/hr.
I haven't heard of Foxcon being in business for many years, so I don't know if their is any legacy service outlet.