1995 Jimmy Runs rough

[soberdude94]

I have a 1995 Jimmy no codes yet it has a rough running engine also it has been surging under load new wires plugs are good I cant get the timming to adjust either I can move the dist. in either direction and it makes no difference how it runs. I also have a vac hose plugged on the driver side it is about 3/8 and there is one plugged behind the distributer. and last there is a port above the fuel inlet on the manifold that is plugged can anyone tell me what that port is for. My Exbrotherinlaw left me this truck when he moved 2 years ago just trying to get it through emmisions so I can use it. I did start this truck at least once a month and let it idle for 15 minutes so it would stay lubed and clean fuel. Any help would be great thank you.