I have a 05 6.0 and when in park or neutral only I can press the go peddle and let off, the rpms will continue for a sec ( like I am pressing on the peddle ) the drop down to normal idle. It starts and drives fine. Truck has been studded, new gaskets, delete kit, blue spring and every o-ring and gasket from top to head gaskets in the past couple months. Any help will be great.