Trying to diagnose rough idle on new engine. New HEI ignition, tested wires, NGK ZFR5N plugs, Weber 38 adjusted to best lean idle and timing at initial +15 degrees. Also snugged down all intake bolts and does not appear to have any leaks. Runs and accelerates great but stumbles a bit when idling. Really bad in gear. Has a Oregon 2106 cam, adjusted lash to .015 IN/EX per cam card while on the stand. Maybe too tight? Other thoughts?