I've read multiple threads concerning problems with 5.4L 3V engines knocking or sounding like a diesel after the engine is WARM....Most people have found the problem to be bad Cam Phasors.
My engine (2004 5.4L 3V) only 'taps' when cold. Definitely more pronounced when lifting off the accelerator. After 3 to 5 minutes the noise will go away (engine warmed up). I've asked my local Ford dealer about my concern and I've been told..."oh thats normal".
I'm running Motorcraft 5w-20 with a Motorcraft oil filter.
Could it be a lash adjuster issue? Please, if anyone has experienced this or know what it could be please let me know. I'd like to point my friendly Ford mechanic in the right direction while I'm still under warranty.

Thanks for your time.

 

Mine does too. Since new. It's normal cam phaser noise. Don't worry about it.