2008 Dodge Ram

Engine Mechanical problem
2008 Dodge Ram V8 Two Wheel Drive Manual

I have a 2008 dodge ram 1500 quad cab 4.7 ltr 2wheel drive 6 speed standard with 10000 miles. About 2000 miles ago, I noticed that when starting the truck in the morning, I hear a tapping, sounds like a lifter. As the truck warms up it fades away but you can still hear it. Sometimes I can hear the tapping in the truck when I am driving. It also has a very rough idle. We brought it to the dealership and they said they didnt hear anything. (But the truck was warm.) They told me it would give us a code if something was wrong, but if it is a lifter tapping, it won't show a code. I was a mechanic at three different dealerships and I know what a lifter tapping sounds like, but the truck is under warranty and I can't do any work to it. Someone said by me using a
Fram oil filter that this may be the cause because it doesn't have a check valve like the factory oil filter, but I looked it up online and it does have anti drain back valve. Don't know what to do. Please give me some feedback on what I can do.