I doubt that was causing a issue, is he getting the tires really wet the co7's are known for crappy shaky burnouts, thats why most get the c06.
Try footbraking the car upto 2500 rpms then letting it rip, it may work. my old goodyears shook bad but nothing like your saying he has. Id bet something else is wrong, does it have a vibration or anything going down the track ?