350 Chevy Miss

Hi, I own an 86 3/4 ton that all of a sudden developed a miss last night. about a month or so ago I put a new quadrajet on it, new plugs wires cap and rotor, fuel filter, air filter, etc on it, and it has run great up until last night when all of a sudden it started missing on what appears to be more than one cylinder, as the engine runs very rough under load, and while free reving. The engine is a 350 with 140,xxx miles on it, and uses a little bit of oil, due to what I believe are the valve guides being worn. I pulled the plugs on it today and they dont look very bad, on one cylinder there is some oil on the plg around the insulator on the inside, but other than that they look ok. I set the plug gap at .045 which is what I believed at the time to be a good gap for HEI. Tommorow I will replace the plugs again maybe going to a platinum plug this time or a colder plug. I pulled the cap which is a bluestreak cap to make sure nothing was cracked or broken and everything appears to be in proper working order. I would appreaciate any comments of suggestions any one of you has. Thanks in advance.

Zachary Sandberg