The launch looks very square for no anti roll bar. You must have the chassis dialed in right.

The engine should live at 7500 rpm but I think you're well past the power peak so that might be slowing you down a tad. 3.90 gears would probably drop you back into the 7000 range which is right around the peak. Changing to a taller tire might be less work, just depends if there is one available that fits your car.