Disabling EGR was worth about 1mpg improvement on my old volvo 240. It also improved throttle response at part load cruise. Definitely worth disabling on some old cars where the EGR was a simple ON/OFF system. The only way to really find out if it helps or hurts your FE is if you try it.
89 volvo 240 without EGR
19/26mpg
89 volvo 240
with EGR
18/25mpg
Model 1 Vehicle Characteristics
Model 1 Vehicle Characteristics