my little car's been running smooth so far... until 2 days ago

that day i had my radiator cap changed, and put in 19L of husky 90-octane.
problem didn't even show up till i started the car up later that night.
car would stall when i decelerate or idle. (does it no matter engine hot or cold)
o yeah.. car has hard starting problems too
pulled the plugs out today and they were black with soot.
also looked at the carb when i shut the car off,
the mouth of the carb was excessively covered with gas vapor...
here's what i think could have gone wrong:
1) fuel pressure too high --> fuel pump?
2) bad gas
3) EGR stuck closed (not likely since there's excessive gas in the carb)
4) choke stuck closed (nope.. i checked it, it was wide open)
that leaves options 1 and 2.
the underlying Q: why is gas being dumped into the carb?
p.s. is there a fuel return line in our fuel pumps? could that be stuck?
what is your opinion, and thanks