hmm not good...

having to much clearance is better than having to less. apparnetly if there isnt enough clearance you can burn the valves out, as they might not be properly closed all the time.

but if you have to much clearance id say you will get excess wear on your cams and shim/valve pusher thing...whatever the cam contacts with (bucket?). that would be the rattles that you are hearing.

i believe you can buy the shims in any size you want, through either toyota or i heard a motorbike shop can supply them as well. but ive never done it though so cant confirm.