Strangely though on the pass before that failed, I did have the afm set at 2 clicks. On this run as well I did much more of a warmup, driving around for 30 minutes or so to try to get the cat hot. It is a high flow cat. Even though HC and CO were three times higher than previous passes they are still only 10% of the allowed limit. Very low and I am not concerned about it at all.
Your exhaust temps were higher before, which could have helped to burn off more HC/CO's, i.e., every action causes an equal but opposite reaction. At any rate, with them being well below average, I wouldn't be concerned either.
I can understand not wanting to replace a $200 valve if you don't have to. But, I bet if you just yank it off every 50k miles and clean it the valve will last forever.
My thought as well, not a lot to one, the main problem seems to be the carbon build up with the small stem port.
I wonder if there is any long-term danger to running without the EGR. Like you said, Toyota likely designed this as part of a system, they didn't just slap the EGR on there to get through emissions.
I've been reading a bit about EGR, and it seems it can actually increase power. It requires the throttle to be slightly more open for a given power output, which can make the throttle operate more efficiently. Also, the reduced cylinder temps can reduce the amount of heat soak happening, increasing efficiency by having more heat go into forward motion rather than absorbed into the cylinder walls. Interesting stuff (to me at least, haha.)
Likely only real danger is to the pocket book due to reduced fuel economy, and the difference in performance that you experienced.
Anyway my butt dyno confirms no ill effects of a functional EGR.
That is the true test w/mods, if you can't feel the difference in performance, the modification is as helpful as 'speed stickers".
