I set the timing with the EST disconnected on my 305 TPI to 6 degrees. Runs perfect. TPS set to .54 and idle is perfect. I plug the EST back in and the car starts to idle rough and backfires. It gets worse the longer it runs but I usually shut it of once it starts to backfire. It ran fine before I began this procedure with a little high idle at start up anytime hot or cold but settled down once I drove it around. When I went to set the timing first it was way advanced when I unplugged the EST. Anyone got any tips or advice.