2000 gmc Sonoma 4×4 4.3

I have a 2000 gmc Sonoma 4.3 with 163xxxmiles on it and I am at my wits end all the sudden it started running really rough missing and backfiring and smells rich when idling so far I have changed cap rotor cam shaft censor crank shaft censor intake gasket set fuel filter cat plugs wires gas spider injectors check compression checked fuel pressure the code reader says random misfire and high voltage b+ ?????? I am out of money and I need my truck been dealing with this for the last 7 months I took bit to a shade tree mechanic and he called me and said “I give up” so I don’t know what else todo but take it to the dealership so if any body could help please