1988 gmc sierra hard starting, running rich

[mragoalie]

I have a 1988 gmc sierra with a 5.0 v8. it has a terrible time starting when cold with me having to crank it for around 2 to 3 seconds or longer. once it gets started it runs fine altough it is definetly running rich jusging by the fumeds coming out the tailpipes. i recently replaced the map sensor, this did nothing after i returned the new sensor i checked the old one again by disconnecting it while thhe engine was running and the idle didnt even think about changing. ive check all spark plugs and noticed that the right bank is black with some being coated in wet fuel and the left bank is white. sometimes i can get some decent mileage but other times i somewhere around 9, city driving. any help is appreciated.