Ahh, the old EGR discussion.  When I acquired my 82 Westy the EGR filter had rusted away so the PO simply plugged the pipe going to the EGR valve and the hole on the crossover pipe with gobs of JB Weld.  I spent a wad of cash on a new EGR filter and crossover pipe to get this system up and running again.  Since I made this investment I have run into many other folks who have bypassed their EGR to save cash and claim it makes no difference.  So here is my take on it.

The computer is programmed to expect the exaust gas to be injected into the intake during heavy acceleration.  The exaust gas contains combustable hydrocarbons that weren't combusted the first time through the combustion chamber.  When this extra "fuel" is not present the system is actually running lean.  Not good.
Additionally, the exaust gas decreases the temperature of the combustion chamber.  This is going to protect your valves and decrease the production of NOx.  In summary, disableing the EGR system will result in premature engine wear, less than optimal performance, and unquestionably increased NOx emissions (i.e. ground level ozone and acid rain).

Maybe the valves are constructed to withstand the higher combustion temperature.  Maybe the amount of uncombusted fuel in the exaust stream is negligable so the engine isn't running lean.  I don't know.  I spent the cash rather than take the gamble.  Anyone out there have some solid answers?

Jake

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