I appreciate all of your inputs, really.
The m104 does have hydraulic lifters. which makes me think that one lifter is bleeding overnight and will tap until pressure will build up. from my understanding, a timing tensioner knock will be noticeable at all time, unlike the lifter knock.
I try to drive it at least once a week, in reality, with snow and salt all over here in jersey , it can take two weeks between drives..
using a long screwdriver against the top of the motor, no noises/taps at idle.
Oil is and was always clean with no shavings.
I’ve read some other posts of others saying the tap disappeared after changing to the delo 400 and driving for a while.
I was able to find a post regarding the timing tensioner which was due for a replacement on an M104 after 200k miles..