The etire rear seat in a Supra, top and bottom, weighs like 26 lbs.
I think a rule of thumb is that for every 100 lbs less weight the same car will accelerate 1/10 th of a second quicker over a 1/4 mile. So theoretically by removing the rear seats you could go .025 seconds faster. LOL Of course you could also yank out the rear seat belts, heavy spare tire, tools and save a bit more weight.
So unless you would put your car on a serious diet (100+ lbs) I would say leave the seats in for the better weight distribution for the launch.