* My intention with this post is to share my experience with the EGR pipe replacement job. It may not save someone else the hassle of doing the job, but it will at least clarify, before hand, what's involved.
* These days I mostly work on '95 and older cars, but I do have several early W210 customers. One such 2/96 W210.055 w/ HFM 104.995, came in with the familiar P0400 code. After replacing the common broken plastic vacuum line near the switch-over valve, and the EGR valve (per TSB on sticking valves), I thought I was done. The car came back with yet another P0400 code.
* I read most everything on the forum related to the EGR malfunction fault and realized that the EGR pipe needed to be checked. I could hear the compressed air, introduced at the EGR-valve-end of the pipe, leaking into the intake manifold. So the EGR pipe wasn't totally blocked, possibly just restricted. I didn't have another W210, with a clear pipe, to compare to. Had read that the carbon restriction usually occured at the intake manifold end. Detaching that end and trying to examine the pipe end, in situ, is difficult and not that conclusive. Nevertheless, I decided to replace the pipe.
* The posts that I read indicated that this was ~3 hours work and didn't require removing the intake manifold. If that fact is true for some models (and I seriously doubt that) it isn't true for the 96 W210/M104 above.
* This job required removing the intake manifold (upper section of two-part manifold) and the injector rail w/ injectors. A reasonable time quote for the second or third pipe is 6 hours. If it's your first pipe, you'll probably take longer.
* You'll probably also want to replace the int manifold seals and the two o-rings on each injector. Don't forget to get a new ferrule, nut, and gasket with the new pipe. To speed up reassembly, turn the clamps on the rear hose of the two intake hose sections so that the clamps can be tightened from below. If you decide to take the resonance chamber off the intake manifold before removing the manifold, there are 4 allen bolts, 2 of which are hidden under rubber plugs.
* The only dimensional difference between my new pipe and my old pipe was a slightly larger OD (+.008in) on the new pipe. The fit is very precise, so bending/reshaping the pipe to remove/install it is definitely not an option. But with the int manifold out of the way, the new pipe fits like a glove.

__________________
ASE Master Tech
Quality Enterprises
Mercedes Svc. & Restoration
Sheridan, IN
317.769.3536