I have 2006 gmc 5.3 multiple miss fires on left bank. Code p300
Changed everything I can think of wires, plugs, manifold gaskets, injectors, Corel, lean
gas tank, check for water in fuel. Sound like a valve in a old style motor. Check com
press on head check ok. Been to car dealer shop threes and not fixed yet. They say it
might this or that but it cost me every time I take it in.