What is the "real world" mileage interval when this engine actually requires the valves to be adjusted? I am at 12,000 miles and using the Wurth feeler gauges, I get a very uniform "feel" on all points when doing a proper check, as I did at 6,000 miles. What are others experiences in this matter and if found to be out of spec, can you notice any performance difference after setting to spec? May as well throw out the same question regarding throttle body sync. Thanks so much to all!