Any suggestions on 2007
 

Sometimes when I slow down to stop my truck starts misfireing, shaking and you can here a pinging sound. It seems too be worse if you pull a load. I've took it to the dealer three times and they say there is no codes coming up. The first time they changed the cam phasers. The second time changed coil packs. when I took it back for the third time they changed the plugs. None of this has fixed it yet. Somtimes when you start slowing down it will have those symptoms and shut off by itself.