Working on a 1991 Toyota pickup 3L V6, automatic. Vehicle has about 160k on it. Valve cover gaskets were leaking, so I decided to change them. While I was there, went ahead and checked the valve clearances. All were in spec but 2. One intake valve was on the low side of the tolerance (.007 -.011") and 1 exhaust valve was out of spec by .001" (S/B .009" -.013") at .008". My question is, do I need to change the shim on the exhaust valve since it is tight??? I've never heard or seen clearance getting smaller over time, so to me I would just leave it. What do you think??