I got the 90 950046 Catalytic Converter installed in my BHR resonated mid pipe. Charles at BHR also supplies a mud pipe with a catalytic converter included but, it’s not suitable for track usage. The HJS cat is track ready and I’ve had mine a year ago.

I tried to follow the advice of TeamRX8 - he knows things.

Edit - my link went to my account so I deleted it - stand by.

https://www.quality-tuning.eu/ca/hjs-universal-motorsport-catalytic-converter-up-to-350-hp-2000-ccm-l348-d130-in77

 

My first plan was to buy the one from rx7.com but then I was advised the orders are not going through currently due to a partnership split.
https://www.rx7club.com/rotary-perfo.../#post12605786

 

i have a track buddy running SCCA time trials in Tuner 4 with header, midpipe, and full exhaust running this X-Force cat:
https://www.summitracing.com/parts/XFO-S0003

He claims it's survived multiple seasons and even a side seal failure. Seems like it could be worth a try.