I bought this sled 3 years ago for my son. He has now grown quite a bit and I would like to add some more power to it. A friend told me to cut open the exhaust can, gut it and weld it back together. So I did, now another friend tells me if I run hard the machine won't have any backpressure and it will burn up my engine. So anybody out there have any advice before we run this sled.