1. is the Emergency STOP Fuel Shutoff on the I.P.
2. The Intake Runners are some kind of Alloy (Mayhaps Aluminum?)
Soaking them in BioDiesel for a couple of days will loosen up all that CRUD.
(I'd be leery of using Oven Cleaner as some have suggested.)
3.You doan Wanna have ANY of that EGR Carbon/Mixed with Oil Vapor CRAP fall into the Engione.
4.GSXR shows in this post all about EGR "Fixing" and CRAP Removal:
Wastegate actuator swap for OM602.962?
He's working on a 602.962 5 Cyl which is the Big Brother of the 2.2L Four Banger in some W201s.
Actually SOME w201s got the 5 cyl 2.5l Turbodiesel, Now that's a fun car with a 5 spd!