My little brother owns a 91 indy 400, pretty nice little quick sled when it's running right. Here's the problem, we put brand new plugs in and it seems to run fine for 5-15 minutes it will then foul a plug out on one side, the same side every time. We put fresh plugs in again and the same thing will happen. You guys have any opinions on what could be wrong? One polaris owner my dad talked to said he had the same problem on an older indy 500, this guy said he grounded the motor to the frame and the problem went away. What do you guys think?