i have a 91 rs with a 3.1 and my right wheel is the drive wheel but after 3 burnouts both wheels were spinning and leaving marks. Why is that?

 

Well after three burnouts (not good for the rear axle) you in fact heated up the tires so much you improved traction to both wheels. Check your RPO list for G80 (limited slip) to set your mind straight, 99 44/100% of V6 cars were not made with that OPTION.

 

how did i heat them up and improve traction to both wheels? The first 3 burnouts i did were only about 7-10 feet and it was only the right tire. but the foruth one showed the left tire as well. and it didnt fade in or anything it was just as visible as the right one. if i were to have heated it up enough to improve traction it probably would have faded in or out not just have cut on as strong as the right wheel. after the forth one i let it sit for about an hour and i tried it again just to see if both tires would spin the first try and it did. but it only seems to do it when i really lay into it more then once.

 

An open differential (your non-limited slip) applies equal torque to both rear wheels. But on slick pavement, the tire with the least amount of traction is the one that will slip, either left or right side. On dry pavement, the right side is the one that breaks free first.
What Blackz87 is saying, is that you heated up your right tire enough to make it stick to the pavement better, which slowed down your free spin on the right side, and distributed some more torque to the left side.
Also as he said, it's not good for the rearend to keep doing burnouts, unless you're goal is to try and break something.

 

oh ok that makes sense thanks