although mine is a 1993, our cars are virtually identical.
Who makes the chip with the upgraded software for the ECM-HFM? I didn't know one was available, or rather I didn't know that there was upgraded software.
I don't really feel my blower motor for the HVAC system is either louder or quieter than any other car I have owned, but I do feel that the highest setting on the blower is higher than any other car I've had the pleasure of owning. When you say your blower is loud, does it make a squeaking noise, or is it loud, like a 747 taking off?
My aspirator fan motor went out, too, and it was squeaking or chirping like a bird. It's located behind the passenger side air vent, and it's not terribly hard to do (after watching my mechanic do it in a few minutes).
About the EGR valve - it's a good thing it was replaced as the original ones had a tendency to stick. There was a TSB in this regard and the part was updated. However, a more common occurence with the EGR system is a blocked pipe. Steve Brotherton wrote an article with pictures in the DIY link at the top of the page. There is a small diameter metal pipe that exits the EGR valve on the passenger side of the engine near the end of the engine block. It goes around the back of the engine, between it and the firewall, and then enters the intake manifold. This small pipe plugs up with carbon from EGR vapors. When a code is tripped, many technicians simply replace the valve, thinking it is stuck closed, when all the while the pipe was plugged up. It is a good idea to clean this pipe at 60,000 mile intervals.
These cars are built like a TANK, and it is the most solid and enjoyable car I have ever owned, and I've owned many Japanese and American cars. However, I don't believe I've ever heard about a rattling in the passenger door. Whatever problem you are experiencing, I can assure you that it is not characteristic of this model. Of the 100 or so W124 owners I've met and talked to at social events with other members of this site and with guys from the local chapter of the Mercedes Benz Club of America
www.mbca.org , I can't recall that complaint once. If you try the search function, you may be able to find mention of it in the archives.
Good luck and feel free to bring up any other issues. I seem to have encountered every problem with this chassis (1993 300E 3.2 / 1994-1995 E320) in my car, and I might be able to help you / save you some money in the future.
Happy motoring,