On my 1996 606 N/A, that would plug into the electric vacuum valve on the underside of the intake manifold and there are 2 of them. The "Y" vacuum fitting attaches to the valve and controls the intake runner flaps.

On my car, all of the flaps have been removed from the spindles. Someone in the past may have just left the valve unplugged to disable them on your engine.

Newer engines throw codes when the valve is unplugged, yours may not.

The head hoisting hole was probably attached with the rear 3 intake manifold bolts. If you are not pulling the engine, you can just leave in the trunk somewhere.

__________________
Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO