on my old 6er i did everything as cheap as possible and it was just fast enough to beet most bolt on 4 bangers. i had a flowmaster 40 series muffler though single exhaust for a lil bit louder sound with 2.5 in piping. a k&n filter to go into the factory housing and took off the cone that goes into the fender. i dont know if that did anything but give more filter to air surface area. b&m shifter.motorcraft platinum plugs. screamin demon wires. eibach sportline springs and a little custom tuning with some basic software to remove the rev and speed limitors.