On a similair note, if you experience the same problems with the Class 4 Fokker 70 in FS2004, please visit that page as well. The thing is that FS2004's flight dynamics engine is totally different from FS2002, therefore a patch must be installed to change the center of gravity and make the aircraft fly correctly.
If you have any further problems with the installation, feel free to email me any time. Sorry for the inconvenience!