Forza Motorsport 2 Car issues.

I have played Forza 2 at least twice now, and somehow my first career was deleted, no biggie am redoing it all over again. Now as for redoing it over again, I do remember when i played the game during my first career and was given the 1969 Dodge Charger I was able to add all the upgrades to it and be able to handle the car no problem and win races. Now on my second career attempt I have done the same exact thing and added all of the upgrades to the car and it slides all over the place now(I know probably what you are thinking, because I just thought of it myself, the upgrade to the game since the last time I played it.) Well... if that is the case, then why is it when I add ALL the upgrades available to the car it is loose as hell? So I tried uninstalling all upgrades and guess what? The same thing!! Loose as hell. How can this be? The upgrades are supposed to improve the car not do 'nothing' to it. I have also adjusted the tuning of the car to accommodate the issues I am having and tried to tweak it but still to no avail...so my question to you all is this: Why have a car in the game with upgrades and adjustments that do not do anything to it whether it is stock or completely upgraded? Sound useless to me, and I really enjoyed playing that car until the game upgrade ruined that.