Wow thanks everyone the help is very much appreciated!

I just thought I would add an update and a little more information. So the motor mounts are basically brand new, I think the previous owner replaced them trying to fix the shaking but to no avail. The cap dance test is quite positive and an oil catch can is definitely on my list of things to do to the car. I replaced all the glow plugs when I got the car, and the very good diesel injection shop I bought my injectors from calibrated and tuned the (brand new) injectors for me before giving them to me.

The first thing I did when I bought the car was a valve adjustment as good ol' ************** has pretty much made me believe it is the miracle cure, and they were right the car had way more power as every single valve was waaaay out. I then I re-checked the valve clearances right before my compression test and about 500km after my last valve adjustment to find they are still perfect.

One thing I noticed is that my glow plugs and injectors have what seems to be a lot of carbon buildup on them since I put them in about 500kms ago, once again this could maaaaybe be fixed by a catch can, but i'm not sure what else it would be as the car makes no black smoke at all.

anyways I really should've said this at the very start but when I did my injectors, valve adjustment, and glow plugs I also changed every single fuel line in the engine bay with clear hose because I had air sitting in the prefilter (highest point before the pump). Since I did that I never really looked at that prefilter again thinking there's no way air could be getting in, I had just changed every single fuel line and copper washer, but sure enough, there is still clearly air in the fuel lines, and no matter how much I pump the primer it won't go away, or if I do successfully get rid of it the bubble is back after a few minutes of idling.

I am very mad at myself for so closely admiring every single detail on my benz but somehow completely missing the giant air bubble that I allready knew was there...

So now I ask all the very helpful people above, how do you find a leak in your fuel system, I just can't figure out where this air is coming from???