I have a 04 chevy blazer,with a 4.3 vortec motor?

my problem i am having is,it pings a little when stepping on the gas ,it burned half of a tank of gas,only drove 100 miles in the city,it has a 18 gallon tank,and only 49,000 miles on my blazer,i can litterly watch the gas gauge move when i drive,seems to idle just a little ruff at idle after that it has plently of power,one time i drove my car,shut the car off then restated it,it acted like it flooded the injectors,i could smell the gas,i tryed to restart my car 3 times then finally started,in my town a lot of peaple in my town drive them,i do not know what is wrong with my car bad gas,or a plugged fuel filter,or just plain crappy gas they sell