I would talk to sw first cause ford isnt gonna warranty aftermarket cats if they are bad. I guess u have two options, 1: put it back to stock specs and if that doesn't fix it take it to ford and hope they can. 2: let sw know the situation and see if they will warranty the left bank cat and if so see if that fixes the problem.

 

Let this be a lesson to all of us boys and girls...

ALWAYS keep OEM take-offs! Find a squirrel hole in the attic to keep them in, whatever, but definitely keep the OEM stuff (I too learned that lesson the hard way with a Porsche fuel injection system that I removed )

Also, FYI, CATs should never go bad. If they do, there is a problem with fuel combustion in the system (too rich or too lean) and it burns out the catalyst material (partly platinum - thus the price)

Hope it all works out for ya!

 

Before you go ordering new cats, have you changed the spark plugs and set the gap to .030"? I'd try that first. Get the motorcraft plugs for the '13 eco.

 

^This. I'm surprised they would even still honor the warranty knowing the ecu has been tuned...

Just another option to getting a set of stock cats- could you find some used takeoff ones that someone has laying in their shed that they want to get rid of?

 

If you have the extra grand to spend why don't you just get a new CAC. I know Franchi sells them and it's supposed to fix the shudder issues....just a quick thought. I have the downpipes sitting in my room for fear of being in the exact same situation as you.