1993 Chevy Silverado Rich Fuel and to much

I having trouble starting my truck. But when it starts it stalls out quick if i don't put the gas pedal to the floor. It ran fine before i replaced the fuel filter and the spark plugs. I ran scan tools to see if there was any problem, but it didnt say anything. I heard that the scan tools don't work on spark plugs for older 1993s. There is to much fuel being released in to the throttle body. What can be the problem