rough idle

my 98 gmc misses at idle but stops at higher rpm anyone help me fix the problem.

my 95 just started doing the same thing... accept mine does not do it at idle it does it at about 1000 rpm but if you mash the throttle it runs fine, does yours seem like it could be a gas or air intake problem? im trying new plugs,wires,cap and rotor this weekend i hope it works...