valve adjustment 2002 corolla

I have an 02 corolla with alot of miles on it--168,000. Engine has some vibration at idle and a bit of a buzz when accelerating. No miss or hesitating.Gas mileage down about 10 to 15%. Also has a tick tick coming from tail pipe. Plugs have been changed.I use synthetic in engine and transmission. Book says to adjust valves every 50,000 but I haven't done it. Could this be part of the problem? What about the catalytic converter? Any suggestions anyone? If valves should be done I think I could do that if I had a little help. I would be willing to buy a reference book with instructions. Thanks for any help.

Wayne

I have a 98 corolla with approx 110,000 miles on it. I was wondering how you have that many miles already on your 2002. Anyway, I have been noticing a ticking noise and power loss along with reduced gas mileage (24mpg in the city which is supposed to be 28 for my year car). I was thinking that valve adjustment is necessary. Toyota said it would cost me $600 to get it done. It is a lot of money but im thinking that since the car is otherwise still in good condition that it would be worthwhile to have it done. Hey let me know if u have had it done and if you have noticed any difference in performance/gas mileage. Email me at dsans61478@yahoo.com if u have had it done. Thanks.