Ultimately, all you need to do is make the car as easy to drive as possible, the 6.5 wont help at all, I run a 7.5 and its more than fast enough...
Regardless of whether the car still wins at the top level or not (it does) its more about getting the car how you want it, the top lads would still be top regardless of the car they drove that season.
Try getting the car set up properly and a calmer motor, that should improve things no end... I used to run my B4 really heavy and it worked for me. (plus lead is dirt cheap and can be removed easily if it doesn't do what you want!)
