QDMx3 only 4 minutes on the ground? Don't go to Southampton, you'd exceed that taxiing out! Are you sure that doesn't mean 4 minutes without the cowls and/or cooling baffles in place cos hot spots would easily be created in those conditions within about 4-5 minutes.
Regarding the advancing throttle, how long does it usually take you to get to the stage where you can advance the throttle without any splutters?