Has anyone tried swapping the primary cats with aftermarket, high flow metal substrate 200 cell catalytic converters and replacing the 2nd cats w/ x-pipe (all weld-in).

I don't want to remove the resonator as I'm hoping to not increase volume too much, while getting the power that's easily within reach. Ideally, I'd like to add a small bit of volume and to keep the system sounding smooth.

I'm fairly sure that leaving the factory mufflers and resonator will keep the total volume and sound quality under control... but if you've done something similar and know otherwise. Your advice is appreciated before I cut her up!

FWIW, I'll be getting an ECU tune as well.

 

I will be the first to tell you that there will be those with limited knowledge and experience who will come to bring their opinions, I will only give you the facts.

Main cat replacement with 200 cell, will increase the volume quite a bit. The factory resonator is good to cut approx. 2.5db (yes I've measured it on my db meter). 2nd cat delete with X-pipe must be done correctly, not all X pipes are created equal, I have proven this, so be careful here. The exhaust design on this car is very tricky to get "just right". I have the 1st cat back prototype from japan soon, that I will be testing/tuning. If you have questions, PM me, I will help you all I can.

 

That is actually a set up that I have been thinking about it. The one and main obstacle that I encounter is not being able to do a simple swap. I don't like cutting and welding. Juswt about every other car that I had the exhaust system is made in stages that you can actually replace individually but not the manufacturers are cheap as hell and they just produce a "one pice" exhaust system if they can.