03 4.6l F150 sludge build up

[Yuk]

I'd throw HPL Engine Cleaner in it. Or Valvoline Restore Gen2.

I'm not sure Auto-Rx worked. There were never any photos or visual indication from anyone that I could remember that showed it was working.

Also, these products need to be thoroughly tested against compatibility with all engine seals. I doubt Auto-Rx had any of that done.

Back in the day (Around the same time that I had 36 liters of GC on my shelf) I ran Auto-Rx in two of my cars.
I remember little amber encrusted chunks of "carbon" in the filter pleats. The Auto-Rx "seemed" to do something.
Crazily, I'm not sure I know what really happened.
Life just seemed to carry on without any real conclusion on that front... I think I have pictures of the filters somewhere.