GMC Repair: Chevy S10 jerking hard when hot, mechanic check, new spark

Question
My 1993 S10 2 wheel drive 4.3 liter jerks terribly when it has run for awhile. In stop and go traffic I have to rev it high and let clutch in and out to move at all. Sputters and pops. Mechanics changed fuel filter, adjusted timing (today it failed smog and 1 degree BTDC listed). I replaced Mass Air device which helped for about 20 miles. I saw sparks tonight at coil and where s plugs connect. Check engine light comes on intermittently when hot and stalls. Ten times to mechanics who I think are not the brightest bulb on the chandelier. Any ideas?

Answer
Hi
You did not say, but has a Tune up been suggested to you?
Sparks from the distributor/coil/plug wires is not a good thing and MAY just be your problem.
I would suggest to you  new spark plugs, plug wires, dist. cap and dist rotor. Also have mechanic check for fire leaking from the coil. If so, you may also need a coil.
Really sounds like you have an ignition miss.
I would, unless you have alot of money tied up in the shop you've been taking it, find another repair facility to bring your truck to. Ask co-workers, friends and family to recommend a shop. You may also want to see if there is any refund IF you've spent money and no difference was made to trucks running.
I really hope this helps.
Just advice from experience.
Good Luck
Paul