I read an article that suggested changing the gyro drift value in the .cfg file to something like 0.125000 from the default 1.000000 in FS2002 to give a realistic drift of around 15 degrees per hour, Can anyone tell me would the value of 1.125000 also be relevant for FS2004?

Gyro drift due to Earth wander (rotation of the Earth) is 15 * sin(latitude). Therefore, if you are on the north pole then the DG will decrease at 15 deg/hr. If you are at 60N then it will be -7.5deg/hr if you are at the Equator it will be zero if you are at 60S it wil be +7.5 deg/hr. But there is also transport wander where you accelerate the error by flying East and reduce the error by Flying West. It is all the opposite in the Southern hem.To test if MS does the Earth wander properly just parkup with the engine running and leave it and measure the error for the time at the latitude and compare to the formula above.Just in case you are interested, Transport Wander = something like E/W ground speed * tan(latitude) / 60