add a glow plug washer/shim under the glow plug, that means there should be two of them. do this for the first tank or when you feel that the motor is well warmed up and running well. then take out th esecond washer/shim and start tuning your motor. this helps because it leaves more room for the plug to get hot and stay hot, either that or you are running a cold plug, and you should be running a med...unless you have a turbo head, then a turbo plug would be the answer.
Hope all this helps.
Take Care and God Bless