Weld representation
Here's the best pic I could get of the weld joint between the CAT and the header. It's not great, but it gets the point across. It's on the passenger side, taken just above the wheel well, aimed down at a 45-ish degree angle, fyi.
To further elaborate on the welding, its going to pure suck if you bring your 4Runner to a muffler shop and say, "Weld please". What I found out is that the muffler shop I brought it to could not "legally" touch the headers and that there was NOOOO WAY the torch would fit where the weld needed to be...not good news at all.
It was originally agreed upon that they'd tack weld everything in place and that I'd bring the header + tacked CAT back the next day for completion. I agreed saying, "I have no other options" and they went to town. 4 hours later they called to say my ride was ready. It ended up that they surprised me and finished it up, not telling me what they did, exactly. I'm cool with that and have a strong hunch that I know what they did anyway. Your welder may not be so friendly, so I'd have to recommend lining that up beforehand OR taking it to someone that can legally remove the headers and weld for you. Maybe you'll get lucky like I did...who knows. If you have another mode of transpo and can kinda weld, tack it in place and then re-remove it to bring it to someone that can weld the rest. You get the picture.
To answer a good PM question, there has been NO SIGN of any "check engine" lights whatsoever. I've driven about 500 miles since the install and haven't noticed anything suspicious.
I'll let you know of any good/bad updates. Have a good one.