Chevrolet Repair: 1996 cavalier, fuel pressure regulator, driveability problems

Question
i have a 96 cavalier that has an idle problem . it acts and appears to be running rich . it even dies at stop signs . it has no smoke from tailpipe when running. have replaced headgasket , o2 sensor  , tp sensor, ics . cleaned upper and lower intakes when off . new plugs and wires . no other driveability problems . does get a 300 code on a regular basis. i know that is engine miss , duh.do you have any suggestions . my next step was to replace the fuel pressure regulator . still averages 33-36 mpg . thanks

Answer
Hi Karl... have you checked the ign system...look at plugs,wires, etc..could be bad ign module or coil. pull plug wires off plugs one at a time and see which one has the least spark or little change in the way engine runs...those cars are noted for bad coil and module...hope this helps