I found a Miata-savvy shop named Xero Limit in the Allentown, PA area.
That shop supports a lot of SCCA Club Racers (which I'm sure is great for them, but it turned out to be bad for me, lol).
It's a very busy shop, so be sure to call early to book your appointment, because the waiting list is long.
https://www.xero-limit.com/contact/
...so, for my situation, I ended up having it trailered to Texas, so the guys who installed the supercharger could dig in and find the issues, fix them, and get my MX-5 ready to go again.
If I find other shops in PA, I'll post them here.