[mreid]

Well, because too small a gap on a higher compression ratio with a high energy ignition (we're not talking your old car points and coil with current resistor set up) will shorten plug life significantly. And I do mean significantly as the plug consumes itself, particularly with a multispark, high energy box on an engine that spends most of its time below 3000 rpm (point above where msd box reverts to one spark per plug per cycle). Conversely, too large a gap will cause misfires, particularly at higher rpms where the charge cycle is shorter causing less energy from the coil.