My truck has been getting harder to start and sometimes stalls when in gear, idling in park or neutral its fine iv recently fitted a new edelbrock rpm proformer intake manifold and new holley 600cfm with vacuum secondries it was fine when I first fitted them now it seems to be getting worse even warm its a ***** to start the plugs look OK I'm running 8 degrees ignition timing new fuel and air filters driving it down the road it goes really well as far as I know its a standard 350 with no internal mods also has a Mallory hei. Any ideas anyone?