1996 GMC Jimmy Truck stalls and once running, it chugs

This has been going on for quite some time and today, it stalled on me where I could not start it again. I had to leave it alone for a few hours and then I was able to start it but it still chugs quite a bit. I had a tune up done a few months back where the mechanic told me that there were 2 plugs misfiring so he changed the plugs and all the cables.
It did not fix the problem. I had the fuel pomp and filter changed on it once when it was bout 60000 miles. Could it be the problem again? I noticed like a humming noise that seemed to come from underneath on the drivers side.
Thanks