Valve adjustment?

So my 98 manual 4Runner 2.7 L, has been sounding kind of chunky when starting cold and idling pretty rough, there is also a slight rattle when I accelerate quickly, at about 2800 rpms, but it disappears after a few seconds. My mechanic says my valves probably need to be adjusted (I've got 121,500 miles) but he can't do it because he doesn't have the right shim kit. I've called around and another mechanic told me I was crazy, and I definitely shouldn't get the valves adjusted. He said just to watch for a check engine light... Everything I've read online has me even more confused - some things (like Toyota maintenance schedule manual) says valves should be adjusted every 60k, other people say they've never adjusted their valves and they have 300k.
I am still quite a newbie, just trying to learn about my truck so I can keep the beast healthy. Any wisdom or insight about valve adjustments would be appreciated!