I have a 17 and have been eyeing this YPipe too. Seems like the O2 sensors are a none issue cause they’re after the 1st set of cats and none after 2nd set. My understanding is the 2 nd set is only for use during startup.

Why not take the stock y-pipe off, gut the cats, and reinstall it? Same concept, may not be bent as pretty, but at least you don't have a pipe right under the tranny pan heat soaking it all day. Free too

There is no heat going to the tyranny at all. Plenty of air gap. The stock crossover is restricted/crushed and severely limits clearance. The only downside the URD Y pipe is I'm pretty sure you have to remove it to drop the tyranny pan.

Anybody have any actual pics of the Y Pipe installed? Such as the gap between the tranny and pipe and anything else that people may find important?

I tried to get some of those up in my build thread. See this post for the install. Of note since then I did add some dings to the bottom of the Y-pipe the other day, I might have to consider a tranny skid to help protect it. I did consider some heat wrap around the Y-pipe below the tranny, but decided it would actually do more harm than good. It would hold in water, moisture, and the dreaded salt mixture to the Y-pipe likely causing it to rust pretty quickly. Without the heat wrap there's better air flow between the tranny and Y-pipe, so it should be able to dissipate the heat, although I'm not sure about how that would work with a tranny skid. That is assuming the skid doesn't rattle against the Y-pipe to start with.
In adding the Y-pipe, Mk3 3" Stainless Exhaust, and MAF converter, power, noise, and mpg are all up. The Mk3 is a little louder than I expected, but only when you're under acceleration or load. Cruising it's mostly quiet.

Running the URD Y pipe without issue for the past 2 yrs.. install post here

Don't expect any crazy gains by itself. You can expect to get some gain up top with a catback setup to free up the exhaust path.

I'm now running a TRD intake with stock catback, headers. I do like the clearance and how it mounts better than the crushed OEM piece. No CEL issues either

Just wanted to share my initial thoughts on my URD Y-pipe.
setup before hand was stock ypipe + magnaflow muffler.
setup now is URD ypipe and MBRP muffler dumping beforte axle.
First off let me just say that if your 4runner is a couple years old (mines a 2012) hit those bolts on the headers with something to loosen it up, I snapped 2 bolts and had to tap them, aside from that easy instal; I took a sawzall to my stock y-pipe to make my life easier.
I crushed my stock pipe and that was the only reason for getting an aftermarket, but goddamn I wish I would have done it sooner. I was sitting at 13.8 mpg before and after resetting my ecu and putting about 100 miles on im at 15.3 You can definetally tell a change in power, I take off quicker.
Only downside I've experienced is a rasp when you get on the gas.

Very easy for an old man just get underneath & check it out tools ie22mm o2 socket & pb blaster ! 2 o2 sensors to remove have spares it you hit them with blaster (toast) ! Urd sends gaskets for y-pipe , really I'm not sure why Op making harder that it seems ? Everything is behind a/f sensors & upper cats !

Quick status report: I have installed the y-pipe and am probably the only member on the forum to do so without an accompanying header or muffler install. It sounds 100% stock again, but there is a noticeable change in throttle response. It's not like VTEC just kicked in (yo) but definitely there.

I will be reporting mpg changes in the near future. Previously it was around 17 mpg (mostly highway with some traffic mixed in). It'll be interesting to see how it changes.

Ultimately, I'm already glad I did it for the improved power (I'll need it in Colorado), and improved ground clearance. Any improvement in mpg will sweeten the deal further.

Ask you shall receive... follow the link. Pics on my build thread

The Build Thread of my Rocky !!!

Ok so your dyno numbers match my butt-dyno feeling, but I'm fairly certain I'm not benefiting as much as you did. This is the only after-market component I have at the moment... The TRD CAI is on its way though!

installed my y pipe and urd hi tuck exhaust. past few days has been no issues and today for some reason i got a check engine light, trac control off light, and the green vehicle on terrain light. Came on during normal driving

Those mods alone shouldn’t trigger a CEL as they are all post cats.

Get a reader on it and grab the code. Must be something else going on.

The only thing that realistically could throw a code that’s related to the install is either an O2 sensor was damaged when swapping it to the Y Pipe or it’s not plugged in all the way.

90% chance, You have a leak at the connection point in front of the rear 02. The slightest leak of any sort will cause this. Triple check the gaskets. and connections..

Also read the code, it is probably something related to one of the cat efficiencies and they will tell you which bank.