Adding weight by adding a roll bar to your car may help more than hurt by stiffening up the chassis. As far as gained cfm who knows as he didn’t provide before and after numbers. I had 4 sets of the Source heads on my flowbench and they all averaged 267 cfm out of the box. Bolting on any untouched intake manifold is going to kill power but easily fixed during your next upgrade. Good luck and have fun.