The nice thing about the Mak's if you still want your Cats you can keep them and put them back on.
Unless you cut it off and weld it back on You might have a tough time gutting the cat that's welded to the header I forget which side it is right now which is funny because I just did my headers but I left the factory pipes connected and just took it out as a unit on both sides. You could just cut off both cats and have new 3" midpipes welded to the headers and to your 3" catback.
True. I probably won't worry about the cats tho. If I gut them, they will pass visual inspection.
I used the same method I plan on doing to my GT on my 2012 GT500. Cut the pipes behind the cat, and use a prybar and hammer to beat the cat material out and break it apart. Then lower the car, get in and crank it, rev to blow out any remaining pieces... raise lift back up and weld pipes back on
I got about 1 tenth and 1 mph in the 1/4. Went to longtubes and I ran the same times but picked up another 1 mph, reason was it slightly better 60ft with the cat deletes every time then with the longtubes. My car is extremely consistent as well, it's an auto. I kind of like the sound with the cat deletes better. What I did was cut them out and welded in 2.5 inch pipe right up to the flanges. The way I did it, it looked factory. I still have them and think about putting them back on sometimes.