Look for a 400 cell metal matrix type. I don’t think any of the available converter is all that high flow, regardless of the specs. I have an Uber expensive racing cat but nobody is going to want to spend $400 like I did. That cat is going on my Evo.
A 400 cell cat will work good for keeping the stink down. I have a mil spec 200 cell on my Evo and it gets a little bit stinky when running it on pump gas. I cant stand the smell of catless cars on pump gas so if that's something you dont like either, stick to the 400 cell. Be sure to do the 2nd cat delete too.