ive got an 05 gt wagon i just got that ran really good but was throwing lean bank code. fixed it with a new beatshcwerks fuel pump, but now it idles and drive fantastic except when i get on it at all. it keeps misfiring in then. i know the main culprits but im just wondering what the most likely suspect is to start. again it only misfires when i put the peddle down halfway or more. if i im just driving around without punching it i get no codes. spark?