hello all, i have a CGC60L S/N CGC470L00509777KF that we are having a problem with. At idle the RPM's are going up and down from about 800-1500, unit is back firing as well. at hight RPM the truck runs great! we have changed the Regulator, diaphgram and cap and rotor. the check engine light is not lit. also is there any way to extract the codes if there are any.

Thanks