My FD makes alot of rattling noises from underneath. I especially hear it in the garage. Also when I shut the car off there is a rattling for a few seconds. I'm guessing its the CAT? Any ideas?

Also, if it needs replacing does anyone know of one that is not from Mazda. Theirs is around $1600 I think. I see Bonez has one for $420 but I'm not sure if that one has more flow thereby possibly making me need an upgraded edu?? I just need a stock type cat, but without the OEM type price!!

any help on this is much appreciated.

 

First, re: the rattle...make sure of what's causing it. Can't be certain of the sounds you're hearing but...the cat had some heat-shielding but so do the turbos around the manifold. If heat-shielding is rattling it doesn't mean the cat is bad.
Re: the BONEZ cat, it's a quality piece and accepts the air line just like stock. I have one on my car that's over 15 years old and still going strong. It is better flowing than the stock cat, but retains enough restriction in the exhaust that boost creep won't be a problem. That typically occurs when someone takes the cat out altogether and puts in a mid-pipe/test-pipe. As I said in the other thread, you keep it at stock boost level, no aftermarket ECU is needed.

 

Thanks Jim. Appreciate the info. I'll check out the shield to be sure.