S-10 Stalls when hot

I have a 91 S-10 pickup V-6 that runs fine most of the time. After you run it on the highway it will stall as you are slowing down. I can pop the clutch and it will restart. Around town it seems to be fine. It only happens when you are slowing down. It will idle fine too! It just had a tune-up. All filters were replaced. Any help would be appreciated.

Just down shift to slow down. You have a manual, use it. You will save on brakes then too. Other than that check the idle sensor, or adjust your idle a smidge higher, just to keep it going at those points where it stalls.

The problem turned out to be the air/smog pump. I picked one up from a junkyard for $25. It runs fine now

Maybe its the air pump given you problems.