92 toyota p/u 22re valve train question please hel

Hello I am a professional tech and have never ran into this..this truck runs rough and clatters badly. I have done chains on these before and the guides look fine. Chain has tension no worries….HOWEVER when I was poking around I noticed cylinder 2 intake rocker had about half inch of play….like with lobe down so I know it will have some slack but I mean all the others can move a bit lobe down. I do not think it can be adjusted that far and also it seems the valve isn’t coming all the way up. Sunk valve? Bad guide? Magically bent? Any help would be great