The "turkey feathers" are there to contol back pressure in the tailpipe/combustion chamber.
In the Phantom the turkey feathers were open at idle and closed (puckered) at somewhere around 75% rpm IIRC (it's been 30 years) on run-up and then opened when you went to burner.
In the mid-eighties when I flew the F-14A with the Pratt and WhitneyTF-30 (we called 'em Pratt and $h_tney's) the turkey feathers were open at idle, then closed at a mid range rpm on run-up, then opened again in burner. As a recognition feature, when closed, the turkey feathers of the TF-30 in the F-14A had a double radius...think like a Weatherby cartridge.
One big reason that the Tomcat went away when it did was that the Tomcat community viewed itself totally in the air to air fighter mode vs the bomber mode.There was a lot of serious foot dragging in the development of the Bombcat along other political considerations mentioned by Jorgei. As we found out later, the Bombcat had great legs and a great bombing system but it was too little too late.
As Rocky mentioned above the afterburner fuel flow in both was on the order of 1400-1500 pounds per minute IIRC. In the Phantom we normally launched with about 18,500 lbs and in the Tomcat and two tanks it was 20,000 lbs. In burner it went away fast.
While training in the Tomcat it was constantly pounded into us not to get too frisky in moving the throttles into and out of burner at high speeds or high angle of attack maneuvering to avoid compressor stalls. Maybe because of that emphasis, in 850 hours in the Tomcat I only had one brief one that cleared immediately when I pulled the throttle back.
I can tell you that on maintenance check flights after an engine replacement I was never as comfortable doing the high speed Mach run or shut downs/relights in the Tomcat as I was in the Phantom.
