I have a 1999 Tacoma Pre-Runner 3.4L. While driving home My Taco.. started to shake, like if a spark plug failed. When the engine is cold it runs like a breeze but when hot it starts to shake. The computer read P306. The mech.. changed the 6th cyl. coil but it's still shaking. He checked the sparks and cables but everything was Ok. I cleaned the injector connector with electronic contact cleaner but did not work. Please help.