1992 Ford F-250 Error.3 Code

Hello,

I just got a 1992 Ford F-250 and it is in pretty good shape. It has under 80,000 miles on it (if you believe it). When I first got it the odometer kept flashing back and forth from mileage and Error.3. The battery had some acid corrosion on it and I cleaned it up with a wire brush, baking soda and water. I replaced the spark plugs, wires, rooter and cap. I got an oil change and topped off the fluids. The error code is still there. The truck shifts a little aggressive into 2nd but not too bad. There seems to be an exhaust leek because it sounds like a muscle car when you accelerate. The RPM reader is wrong because when I am in idle it reads 2-3 RPM which can not be correct. When I hook the truck up to a diagnostic reader it comes back with a KOER 32 code which references and open EGR valve. Any idea what this Error.3 code is or is it a vague code? Thanks