I have a 93 chevy 4 wheel drive pu. odometer says 250,000 not sure if original miles on engine. i am getting a code 32 egr failure. i have replaced the egr valve the egr solenoid, tried a different used 02 sensor, cleaned the connections on the ecm. replaced a ground wire from cab to engine block. i am still getting service engine soon light evertime i drive. any info. on other possible things to check or replace would be greatly appreciated. thanks,chevypu