Wow, this thread is a bit old but here goes:
Looking to change my cat after the relevant CEL came on and after having done the CO2 test (max limit is 0.55 and I'm on 1.5-1.9) Based in Germany. I got in touch with HJS Germany and they recommended HJS article 90950166 (connection 76mm) for me. It costs 550 euro. I read about the HJS cats on the forum and it seems people are happy with them. Has anyone had an experience with this particular article 90950166 though?
I also found some cheap options on ebay like this one:
https://www.ebay.de/itm/Walker-Katal...frcectupt=true
And this one:
https://www.ebay.de/itm/KATALYSATOR-...frcectupt=true
What do you think?

 

Cheap cats die quickly when connected to a rotary engine. The exhaust is just that much hotter and there are more hydrocarbons in it.
Spend money on a quality product once or spend money on lots of crap products when the catalyst keeps dying.