Now what size wheel are you running? If its an 18 in wheel i would say try raising the tire PSI up. I run mine aorund 18psi normally and sometimes up to 20psi after a burnout and i have pulled several low 1.7's and a 1.69 on em.
If you are on a 20 inch wheel then keep the tire pressure higher. closer to 30.
But as far as launching technique i too have a manual so i cant recommend anything but more seat time.