94 caravan NEED SOME HELP!!!

im not sure what it could be but if im going down the highway and let off the gas, the rpm's drop to lower than 500 and bounce back up again. It has about 140,000 miles on it and i just replaced the O2 sensor. the spark plugs and fuel filter has also been recently replaced. I ran the scan and got the code 32. I am not sure what that is. If someone could help me, i would really appreciate it.

code 32 is a egr (exhaust gas recirculation) circuit problem.

Its either the egr solenoid or a malfunctioning egr system(valve)

The solenoid should be tested first and if functioning properly the valve could be clogged open or shut.

This would cause the dropped rpm due to improper air fuel mixture.
hope this helps.