Just some information that might be useful to someone:
My second-hand '05 V6 4Runner (145k) recently was experiencing sudden power losses when accelerating or ascending hills, and loaded. Each time it happened was on extended wildland trips with a lot of gear.
Engine light, VSC Trac and ABS lights would come on. When I pulled over and let ii sit for a few minutes, it would run fine, but the warning lights would stay on.
Two dealerships diagnosed clogged catalytic converters. I had both replaced, with sensors. VERY expensive. (Please don't chime in with shade-tree solutions I could have chosen ...).
Neither shop asked the larger question: Why did the cats clog? As we all know, troubleshooting is the apex of the trade, and not all mechanics are up to it.
It happened again after the second cat (with sensors) was replaced, and again while loaded up and ascending minor grades.
Many hours spent watching YouTube videos addressing the very symptoms I was experiencing led to the conclusion that the problem was dirty and sticky variable valve-timing (a.k.a. oil control) selenoids/valves.
Among the cautions YouTubers noted was that the VVT valves can be VERY difficult to remove, even to the point of having to drill out the centers and using an extractor supplemented by cursing.
An independent shop known for expertise with Toyota trucks ran the usual diagnostic tests, but the warning lights had turned themselves off. They could get no trouble codes. They tested the VVT selenoids, and indications were that they were working. (Key here apparently was that testing the electronic selenoid wasn't the same as testing the mechanical sliding valve it activates.)
I didn't buy those results. So I insisted that both valves be replaced regardless of their test results. Being in the
wildland-travel business, I cannot have an unreliable vehicle. (I own three 4Runners due to their usual reliability.) It had to be fixed.
Both valves were difficult to pull out. One broke. Once removed, we found that one valve was completely stuck and likely was not functioning; the other was notchy and sticky, and didn't slide smoothly at all. Both were dirty with that brownish varnish, likely because the previous owner (soccer mom) drove it for short errands and didn't attend adequately to oil changes.
YouTube was right, and we all learned something. The truck is running well now, and reliably. MPGs have gone from 16-ish to over 20 often.
I hope this is helpful.