Old post did you ever get this resolved ?

I've had the same problem with both a '94 C2500 and a '96K3500. Act like they run out of fuel under load or up hill. '94 injection pump went out shortly thereafter (was a cheap rebuild) and the '96 has a rebuilt pump. Runs fine empty or down the road, only acts up under load, or as mentioned before, up a hill.

daCat

Check this thread https://www.dieselbombers.com/chevy-...when-cold.html to check fuel lift delivery to your IP a starve IP will cause poor power.