Thank you haasman for going out of your way to answer this post. You've been very helpful.
I went into the rehabiliation of my car's suspension in the hope that all the annoying sound i hear from inside the cabin will disappear. When I bought the car there were a lot of rattles, vibrations and cabin noise that i don't know from where the hell it was coming from. In my experience of riding my friend's 300E, i should not be hearing any noise at all except the, sound of the engine, stereo, the aircon, my voice as i sing along with my favorite tune and usual the "thud" sound whenever the car goes through bumps, this was even at a time that he has not changed the front shocks to HDs yet.
First, i started replacing engine mounts, transmission mounts and timing chain.
Second, replaced the front lower ball joints, tie rods, center links and idler arm.
Third, overhauled the brake calipers
Fourth, tightened and lubricated door panel screws and links
Fifth, was the recent repairs i stated at the beginning of the thread including bolt tightening underneath.
These all came from the knowledge i've so far gained from this site.
Don't get me wrong, but i've been satisfied with the suspension repairs so far and i admit that the car is a far cry from its original state from whence i bought it. There are bumps/road imperfections that make me smile because the car already manages it so well (very quiet , indeed, again except for the solid "thud"). However, there are bumps/imperfections, that does not feel well with the car where I still hear a lot of noise from underneath (front). Thus, the question "am I missing something".
Greg, to answer your question, yes, my car model had the rear self-levelling suspension. But I think the PO, instead managed to have it installed with an ordinary bilstein hd with no ill effects so far. My problem, however, is in the front and i dont have a bouncing issue, front and back. I'll be trying to, revert it to the rear self-levelling mode in the future if my budget will allow it since it will cost me about US$1,500.00 more.