95 sonoma running rough

i have a 1995 gmc sonoma with a 4.3ltr 2 wheel drive. i reciently did a tune up on the truck, plugs, wires, air filter, dist cap. ran fine for about a week and now it runs rough, constantly dying. pulled out the spark plugs to find they were black. therefor i changed the co2 sensor, and the map sensor. to c if there was any difference. tiny bit better, only on the inital startup. thought it was the fuel filter, changed that, made shure gas was being pumped. ran a code reader, but came up it wasnt communicating with the computer. do i have a bad computer?? is there a check method i dont know about?? any sugestions??

Welcome to AF, some code readers will not work on the 95 transition year, you will need a full scan and pay attention to the coolant temp sensor readings, also check fuel pressure at the rail, no quick answer here.