Set the BP for the Engine to augmented = True. That activates the AB itself.
Then go the Engine XML file you are using. Make sure augmethod is set to 2. 2 sets up Throttle so that when Throttle = 2 afterburners are activated.
Option 1 works as well. but not as well as the 2 method for now (probably just understanding for now).
Lastly, I set ThrottleData MaxValue to 2.0. That got the plane moving up to around 760 in straight flight, so I will play a little more later tonight and try setting it to 3 or 4 till I get the top thrust speed I need for that plane. Not sure this is the best way, but at least it seems to work. If it does there should be a way to have a formula figure out what this value should be based on known values.
Currently, I am using a joystick with a single throttle, I do not have anything to set FULL throttle and a separate AB switch.
EDIT: I did get time to change the value to 3 on the ThrottleData and increased the AB to 1000. This should allow the creation of controlling the AB thrust incrementally as well.
On a side note, I am not finding where/what I need to change for the shaking. When you have time would you mind showing me a little more on how you implemented that?