I was doing a power brake in my 98 supercharged cobra and when i let off the brake and slammed down the gas it kind of sputtered a little and then climbed thru the rpms to backfire....so i let off and hit 2nd and mashed it and it kinda had power and then dogged out a little....think its my plugs? Am I running lean? I am looking to get it dynoed here shortly...Any comments on this would be greatly appreciated. Car has run fine for the rest of the day, of course I took it easy on her on the way home.