I would suggest getting a chip to switch it off for the 89 as well. Some folks that obviously know way more than I do will suggest you don't need a chip and you can "short" out the EGR sensor fooling the EEC so you don't get a CEL, but the result of that is running a more rich or leaner AFR because the EGR sensor never changes to the environment.
I know its an old thread, but who would I talk to about getting a chip? My EGR is broken and I plugged both ends but I've been running without a chip. Also how much would it run?