valve adjustment
 

I have a 97 4runner, 2.7 4 cylinder, very good vehicle with very few problems. The exhaust manifold cracked at 100K, but now the check engine lite came on and the dealer claims I have low compression on #1 cyl. 98 lbs and causing random engine misfire code 301 on OBD could the valves be burnt or they just need adjustment? They tell me I need a 3000 valve job. If this is true, maybe valve adjustments should be performed more often than they recommend, only if they're noisy, but tight valves don't make noise they just shrink and get whacked. Any suggestions???