Black condensation from the muffler (rounded or oblong housing at the front of the tailpipe) is normal until the engine and exhaust is fully warmed up. During very cold weather it may continue for a longer period of time. The hole where the liquid in dripping is there to allow the condensation to drain out of the muffler, it makes the muffler last much longer. Don't replace unless it has a hole elsewhere and can be heard.

The gas smell is likely a rusted component in the fuel system, very dangerous, get it to a mechanic.

 

I have a small hole on the bottom side of the muffer (2000 Blazer 4.3 4x4 LT 105K) and it seeps out of there and sometimes its like a black grit (Very hard to get off the garage floor, also when going down the highway when My speed gets up to 80, I can hear the exhaust get louder. I'm thinking new cat and muffer among other things that I have put off. I have purchase a new Nox, LTZ and it goes in the garage now and the poor old 2000 gets the out doors and I think its mad at me. If I don't start it everyday, it gives me problem starting, like a leak down in fuel pressure. I'm guessing the Pressure Reg and I'm not to thrill about changing that out, at 64 yrs of age, things just get harder and a whole lot slower..hahahahahahaha.