The tach sender suffers from poor solder connections, and if they are bad enough, the cigarette butt fix won't work -- it puts pressure on the connections to hold them together.

The EGR reduces milage and power a little, and can cause horrendous smoke and drivability problems if it sticks open. I would imagine the PO disconnected it to either increase performance or "fix" a defective valve. If it works OK connected, leave it, or you will fail an emmisions test one day.....! If you get funny engine rattle and huge clouds of smoke at low speeds, it is sticking open and needs to be replace. Ditto if there are soot markd around the base of the vacuum can -- the shaft seal is shot. If you don't want to fix it, at least plug the line with something like a BB and put it back on the valve -- since you live in CA, you will get fined for having it disconnected if you get stopped for an emmissions check!

I have plated the one in the Volvo off, pending finding another one that costs less that $400!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!