340 Chugging instead of Reving

I'll assume the needle inlet valve isnt stuck pushing fuel out ththe mains and flooding it?
Its firing, it wouldnt be blackened plugs otherwise..they'd be wet, maybe..but bone white if no ignition was present...or also if an exhaust valve wasnt closing..no color. Things you might do...nipple plate off the plenum...then take the rockers loose to close all valves...then pull vacuum against the intake valves. That will rule out leaking intake valves, intake seal.
Check engine ground to chassis ,plugs tight enough to break the paint and ground, box grounded, coil isnt rapid firing 'had this problem with an msd blaster before'. Does it even run good on starter fluid?