Unfortunately, you are only going to get speculative answers here or any other blog/forum. A "leak" is on an individual bases. Everybody has a different circumstance. Leaks come from different places at different times on different days from different temps etc.
If you have the ability, you are best ...

I concur with mr rick as these types of issues are nigh impossible to diagnose without physically being there with experience to see
the possibilities.

Does it have daytime running lamps?

Looks like the stud for the manifold heat shield. Not the manifold itself. There was probably galling and it snapped when being removed.

Go with bilsteins on the front. B6's there not cheap. Ball park 240-260 usd.

What other symptoms are you having with the electrical?

Replace the MAP sensor.

Control arm bushings.

Try putting the key in and turning it to the 1 position and leave it there for a couple of minutes. Then move it to the 2 position and leave it there for a couple of minutes and then try starting it. Position 1 couple of minutes, Position 2 couple of minutes, and then start. All without
turning the ...

Driven racing oil DT40. The type of oil you choose should come down to how, where and when the vehicle is driven.
How: heavy foot, track days
Where: tons of city driving vs mostly highway etc.
When: Is it primarily a summer car? or does it see four seasons? Are you willing to change the oil to match ...