I brought my truck in last week and had the valves checked and adjusted. My T100 has the 3.4 with 122,000 miles on it. The cost was $276 for labor and $24 for shims. When I asked about purchasing a shim kit they told me that the kit sells for $30. The valves are a little quieter after the valve adjustment. I haven't noticed any increase in power, it is more preventive maintenance so the tolerances stay in spec and the engine dosen't burn a valve. I read through old posts here before having the work done. It seems that at least one special tool is needed to access the shims and based on the time involved and my level of experience, I decided to have the dealer do the work.