2011 5.0 a6 with steeda cai, pypes x-pipe, magnaflow over axle and muffler. When rps sit over 3k for some time and let car engine brake I'm getting the wonderful blinking engine and cyl 4 misfire. Dealer replaced coil and plug last week. Still getting it. Code has not hard set since coil and plug were replaced but I usually get it at least once a day. Any thoughts? Just uploaded my tune today from Kevin. Any thoughts?