I have a 1996 E300D. I did a bypass which should have no effect on fault codes and also ensures clean air delivery to the EGR. This is done by:
1. remove the metal connection tube; use a pretty thin piece of metal/aluminum to cover the exhaust side connection - retaining the use of the factory clamp. Use high temp RTV or ceramic wool insulation for a gasket...
2. Next, cut off about a 3" long section of the metal tube (from the longer end).
3. Bore a hole in the air cleaner box, above the air filter - about 1" diameter, in order for the newly cut tube end to pass snugly. Using RTV again, insert the tube end from the inside of the air box out, using RTV to seal/lock it in place. Allow to dry overnight.
4. Buy a 24" x 1" diameter rubber auto grade hose. Reconnect the original factory connection to the inlet of the EGR. Install a hose clamps to each tube end, slip the hose on and tighten.

You now have a guaranteed clean air supply to the EGR. I will not get into the benefits of a high grade air filter in use with an EGR dumping LOADS of crap and soot into the intake after this filter...

Good luck!

Scott

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