1992 190e 2.6 M103

I'll try to keep this post balanced .. too long, people gloss over the details, too short people ask for details.

Trying to troubleshoot a rough idle. Stutter is hardly noticeable in park or neutral, stutters excessively in drive or reverse. Car starts fine cold (albeit now with the temps really low it requires some effort) and idles fine cold. It's when it warms up that the problems arise. Car drives fine once RPM is up so good on the highway, cruising, whatever. Accelerates consistently on the highway, does not bog.

Things I've done in my 2 years of ownership:

- All ignition components including non-resistor copper core plugs (have not replaced coil however)
- O2 Sensor
- Fuel filter
- Air filter
- Coolant Temp Sensor
- OVP
- I've removed the ICV and watched it click open and closed with a 9V battery so I assume it works (just a couple of days ago)
- I have sprayed carb cleaner all over the damn place underneath the airbox and I couldn't really register any change in idle. I did not spray the EGR and now I'm thinking I should have, would that be a good test?

And probably a bunch of stuff I'm forgetting. The rough idle is a stutter, not consistent rough idling and really only when warm. Lately it's progressed to stalling when putting it into gear. Idles fine in park or neutral, idles like crap in drive or reverse, sometimes stalls when shifting into D or R, sometimes stalls at lights.

If my EGR was stuck open I've read that would be a massive vacuum leak. I keep reading references to vacuum testing the motor but I don't know where to plug a vacuum gauge (I have one). My car does not have an economy gauge. I have drawn a vacuum on the hose going up from the EGR (to the check valves or whatever along the firewall) and either there is a big leak or no vacuum is supposed to be present there. What does a vacuum leak here indicate?

IF my EGR was stuck open, would it affect the cold idle as well?

What vacuum port can I use and where is it, to test my engine vacuum?

My fuel economy has always been crappy on this car.
Compression is 180-185 across all cylinders.
I have read numerous threads on rough idle and there is always a lot of conjecture and "throw parts at it" suggestions and that's not what I'm trying to do, I would like to know how to go about troubleshooting this in a systematic way by eliminating variables.

There is a faint exhaust smell in the cabin when stopped at lights, is this a clue?

Thanks

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1992 190e 2.6