Any ideas what's going on with my quarter miles times? I have a 2003 SS with 115k, it's got a K&N cold air kit and a dual in/dual out thrush muffler. I took it to NE Dragway Wednesday night for the first time since I bought with 107k. Out of four passes, the best it could run was 15.89 @ 85 mph! Needless to say I'm concerned and disappointed. These are supposed to be almost a second faster out of the box. WTF?