what do you guys think of these?

My understanding is that you will CEL issues due to the O2 sensors.

 

And if there's room, you can back out the O2 sensors with the non-fouler trick and still see a voltage wave over OBD, just at a lower level on peak. It works great on my full 2.33'' dia stainless system on the Miata with high flow cat from Roadster Sport. I can see the data clearly on OBD2 and Torque App. Two non-foulers were required, Drill the first, insert into the second, then insert into the pipe bung. May not be enough space.

 

Randy.

I have a set with ceramic coating in excellent condition I'm selling if you're interested. Just PM me. I've gone back to OEM cats. However, you should be aware, as stock, these need to be field modified a bit so they won't hit the rear motor mounts and their center bolts. Mine already have been done so professionally at a machine shop. If you look close at the pics, you will see they are made round and concentric with the inlet / outlet pipes. The OEM Ferrari cats are oblong and not concentric with the pipes for this reason. The pipes enter at the bottom of the cats thus raising them up. In order for these to fit on a normally set up 355 , they need to be depressed slightly on the bottom about 3/4". This gives enough clearance so they won't ever hit. Otherwise they're fine, well made and sound great. The rear flanges that clamp to the muffler are just pressed on, albeit very tightly, but can be adjusted to facilitate alignment if needed.

 

I forgot to mention, to avoid trouble with CEL's, you need to get some "L" shaped extenders for the rear O2 sensors to back them out of the exhaust stream. That's what I used and they worked well. Unfortunately I don't have them anymore but Fabspeed sells a nice polished SS pair for about $150 if memory serves. You could also make some up yourself if you don't mind something less refined than the Fabspeed ones.