Intake manifold is plastic...Good reminder. I would really kick myself if I heard it crack.
The two hoses at bottom of intake manifold...I had to replace both of them because they were hard as a rock (one broke on removal, the other broke on reassembly) BUT I never thought of checking whether I broke the plastic neck they fit on to. That is very much the area where the carb cleaner spray gives a reaction. Early on in tracing the leak I thought I didn't have a good seal on one of those hoses so I replaced the spring clip hose clamp with a screw tightening type - now I'll check the plastic neck to see if it is cracked.

I didn't replace the injector O-ring seals so I'm not going there.

When i did my head-gasket, that area broke because it was so brittle...JBWeld took care of it...

Most of intakes break around that area because of the damn original hose clamps...should definitely inspect it and see what you find. buy a cheapo telescopic mirror and flash light if you don't have one

good luck

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1993 300E, 2.8 M104 .....

I haven't been able to work on the car, its been too cold, windy, rainy , whatever...
For the cheap cost involved I might as well just apply JB Weld and see if that does the trick. If not I'll keep looking for the leak.
So where to apply JB Weld?
Take the hose off and apply on inside of neck dabbing on with finger or on outside of plastic neck? Apply extra at the base?
Who here has done it....tell me how you did it.

Well it's going to be tricky with the manifold on the car. Mine just slap busted clean off the a manifold, as I said, so I glued the whole thing back on, which means it is glued back on with a fillet of JB Weld all around it. Mine busted off below the rectangular base of the two hose connections, where the base is mounted on the manifold. If you look in there, you'll see the two connections/spigots sticking out of the rectangular plastic base.

Since mine broke off there, it is reasonable to think that is a weak spot, so put the JB weld all around the base of the rectangular part where it lies on the manifold. Make sure you clean the crap out of it or else the JB Weld won't stick. I would blast it with brake kleen and then swab it good with q-tips saturated in brake kleen. You could also use lacquer thinner. This procedure will also etch the plastic and roughen it up a little which will aid the adhesion of the JB. You'll need to use a mirror to see the back edge of the rectangular base part up against the intake. Mash the JB weld in there good with your fingers. You can wear a latex or nitrile glove, mash the JB in there, then smooth it out and press it in there good with finger dampened in lacquer thinner. Spit also works for this.

That is what I would do. Since you can't access this very well I think you are going to have a tough time adequately getting the JB in there. But it's worth a try, it's cheap, and you got nothing to lose but your time. Let us know how it works out!

I finally found the source of the vacuum leak: the smaller breather hose has a nasty gash in it. So how to replace that hose?
I removed the actuator on top of the throttle body and now what remains in my way is the upright (3" diameter) tube going to the throttle. If I can get that out I may have enough access to replace the breather hose. I loosened the hose clamp at the bottom of the upright tube and can now turn it in place but something is preventing it from coming off. That upright tube has ears at 2 corners that I can see so I turned it to different positions but can't find a position that allows it to come off.
any help please?