Not too sure how I can help here, all i know is that when I used to be into drag racing, I adjusted the suspension so that the front end was as close the the ground as possible, and the rear-end was as high as possible, along with really tough suspension. Added to that, a little bit of ballast weight between the middle and rear of the car. It worked well for me, helped me achieve top speed and made the car aerodynamic. It's worth a try, if you have no luck then apologies. (Use racing:soft tyres, it makes a huge difference)