Actually, it probably isn't a model problem . . .
have to hit "I" in order to see the AB, but when using Viper or Typhoon all I have to do is max power and the flame comes out
Meaning you have succeeded in adding ABs to another aircraft? That means you are using fx files to do so, and any fx file can be activated (through the smoke system) by a gauge you can add to the aircaft's panel.cfg file, which is probably how the Typhoon and Viper do it. Not being a military aircraft fan, I wouldn't know.

What I would suggest is you get CfgEdit, which is a freeware panel creator and open either the Viper or Typhoon panels and see if there is a gauge in there that doesn't seem like it belongs (such as being in a useless spot and really small). This usually means its a gauge with functions other than telling you how an aircraft is functioning. Copy that gauge (Ctrl+C) and open the panel.cfg of the aircraft you are wanting to add the ABs to. Paste the gauge in and put it almost anywhere (it will be invisible in FS). That should do it. If it doesn't work, come back and we'll fix it . . .