Awhile back I posted a thread about a "ticking or tapping" noise from the engine. After I had the dealership replace a failed injector a tune-up was performed on the truck. During the tune-up the injectors were flushed, all spark plugs replaced and various other adjustments etc were performed. Well after the tune-up the ticking/tapping noise started. I took the truck back to the dealership numerous times. The dealership blamed the cam phasers for the noise and replaced them. Still after the cam phasers were replaced, the noise was still there. I ended up taking the truck to a second dealership and once the valve covers were pulled, the #1 and #5 spark plugs were not even finger tight. The noise were the spark plugs arcing. I had the first dealership (the dealership that did the tune-up) replace all eight plugs. Amazingly the noise disappeared. Just thought I'd let everyone know that it is always good to get a second opinion on work that is not performed correctly!!! I thought that taking the truck to a reputable dealer that the work would be done and done correctly. Well I was sadly mistaken.