Ok, I finally found something.

I did the smoke test, and I found one leaking fuel injector port. But then I noticed more leaking from under the air flow sensor housing. I decided to dig deeper. I removed it (getting easy at this point), re-seated the fuel injector and did my smoke test again.

I found a leak on both sides of the throttle body where the shaft comes out and attaches to the throttle linkage and where the position sensor is fixed.

Questions:

Is this normal?

Can this be rebuilt or do I need to find a whole new throttle body?

During my smoke test I had smoke coming out of the valve cover. Is this normal or should there be a check valve in between the intake and valve cover?

There is a PCV valve between the intake manifold and the valve cover, but it only closes when the engine is running and the throttle plate closed. The valve cover and oil filler cap should have a good enough seal to prevent smoke rolling out. The valve cover will fill with smoke during a smoke test due to the PCV breather connecting to the intake manifold.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Sorry, I wasn’t very specific. Smoke was coming out the hole where the breather line attaches. The line that goes from the valve cover to the air filter housing This

It sounds like this is normal.

Also, I have replaced all the hoses and lines as well as the valve cover gasket.