Car in question is a 1983 300D turbo with circa 174K on the clock. I have had it about a month, and it has always had a bit of roughness or lope to the idle. I have tried quite a few small things so far (all filters, new push-type primer, cracked all of the injector lines), and the idle will sometimes be better when it is cold. For the first time today, I noticed the cigar hose (return line) pulsing in rhythm with the idle. This means the fuel pressure returning to the tank is oscillating - I wonder if this could be the rack dampener bolt (definitely still the old style mounted on the car - not the new gold one)? Any thoughts? I've also got some nailing when it is cold, and a little nailing at mid-range (1,500 rpm give or take) occasionally (I'm thinking time for some new injector nozzles).