Hi guys!
I hava both FS2002 and FS2004. I modified the dynamics a bit to both versions, and made available at EHM website. I must say too, that I do not have any problems with the plane.
Could you tell me more circumstances about the problem? For example do you use the afterburner for supersonic jump? Usually I start the flight at FL350@M0.9, when I turn on the afterburner, gain some speed and then start to climb. Climb rate is about 2000 fpm. If you climb too fast, the bird lost speed and may fall down like any other plane. But if the climb and acceleration goes parallel there will not be any problem. At around M1.7 you can turn off the afterburner and it will blast you until M2.0. Of course, in the final phase you should decrease the climb to 1000...1500 fpm.
If this "tactic" still do not help you, probably an add-on messes on your FS installation. Maybe FSUIPC, or a bad panel, or some weather add-on...I do not know.