94 GMC Sierra not running right, need help
 

I cant figure out whats wrong with my truck, I have to pump gas to start it, sometimes it idles bad, it spudders while driving, hesitates and rpms drop when i punch the gas stalls out when stoped, seems to be worse the colder it is outside. Ive changed fuel filter, spark plugs and wires, distributer cap and roter. any ideas I dont know what to do next.

Check for a vacuum leak at the base of your throttle body by spraying carburetor cleaner around the base. If the RPM changes when you spray the cleaner there, then you've got yourself a vacuum leak!

Have you checked your fuel pressure?

someone checked my vacuum for me and told me that there was no leak.
no i havent checked the fuel pressure.
And i forgot to mention when I bought the truck it was sitting for about 2 years

Have you put new gas in it yet and run it for a while?
TB may be plugged up from sitting and need cleaning/rebuilding

Yeah you could very likely have bad gas in there ... gas can go bad after just one year. Plugged fuel filter perhaps too.

Ive had it for about 6 months now, changed the fuel filter 2x.
Could the fuel pump get cloged up from sitting?
there were times the truck would run great, then all of a sudden back to crap again.

Yeah definitely check fuel pressure, also is your check engine light on at all?

It must be a fuel supply issue... If it won't start unless you pump the throttle? And it runs good periodically.... This could be a sign the fuel pump is on it's way out, or the fuel pickup is beginning to plug with slug or rust.
There is possibly a fuel filter under your truck on the frame rail and a smaller one at the throttle body.
Another possibility is the two injectors are beginning to clog

ya, the check engine light comes on randomly

Scanning the codes wouldnt hurt