Tu-144 handling problems

Hey folks, I downloaded a Tu-144 from simaviation and having a hard time controlling the aircraft in flight. It's flight characteristics resemble that of a cow, not an SST. The aircrafts cruising speed is about 1020 and altitude is 17km (about 53000). However this one doesnt want to go above 27000, when I reach that altitude it starts 'choking', its rate of climb is fairly shallow but it is LOOSING altitude when I try to get higher. The other problem is the exact opposite, when I try to land it, its too fast. I descend with IDLE engines, and the thing overspeeds like mad! Its speed simply doesnt drop below 390! I have nose down, gears out, it barely looses speed! Is there a problem with the Flight Dynamics? If anyone wants to download it and try (I recommend it, the plane itself isnt that bad) here it is http://www.simviation.com/fs2004jets56.htm