at the end of May, my blazer developed a condition to hesitate and stumble and miss. which was later found out to be an Electronic Spark Control Module, my mechanic bypassed this. in about a day the blazer came back to life and ran great. about 2 weeks later it started doing it again. so i ran the tank of gas(87 octane) and put in 93 octane, after the rest of the 87 cycled out, it ran great again. the next time i filled up, i put more 93 in and it ran like ****. and currently still runs like ****. stumbles, loss of power. low rpm it stumbles and such, and at WOT it stumbles. so one night after i had been driving i shut off my truck and popped the hood and noticed that the overflow canister had gas around it. this had lead me to believe that my truck is running rich. the bad news, i do not know how to adjust a carb and i really don't have any money unless i can get my parents to help. i also think that my catalytic converter might possibly be plugged.
any ideas?

305ci with a 4 barrel carb

also, spark plugs were changed at the end of may by myself, the distributor cap and rotor were also in good condition.

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1985 K5 Blazer Silverado
5 liters of V8 fury.

do any of you think it might be the pcv valve? that's never been changed and i have no idea what the hell that even does.

alright, went to the gas station today because i had 1/8th of a tank. just as i was pulling into the gas station it seemed to be running fine, i put some 89 octane in it because i didnt have much cash. i start up, leave and the damn thing is running absolutely fine. so i drove around for awhile. when i got back home it seemed to be acting up just a lil bit. doing the same thing as before, bogging down, stumbling but not as bad as usual. what the hell is going on?