'99 Sonoma with 4.6 V6 engine, automatic transmission. This morning, cold start (20F), engine died twice immediately after starting. Feathering throttle kept it running until warm, then no apparent problems. Returning home tonight it started fine, then I noticed it was starting to cut out at higher rpm as transmission was about shift. Got to a side street with a slight uphill grade, shifted down to 2nd, and drove the grade under medium acceleration produced considerable cutting out, almost sounded like backfires in the exhaust but felt more like fuel or air starvation. There are no codes showing. I noticed a sulfurous smell in the exhaust upon parking. Intake manifold gasket was replaced about 2,000 miles ago, engine has run fine since then. This work included a new rotor and cap, but I noticed it was not as immediate to start as before the work. I suspect a sensor of some kind, perhaps collant temperature, or fuel pressure? Last fuel fill was about 100 miles before this happened, so I do not suspect bad gas as much as I would if this had happened immediately after a fill-up. I use 10% ethanol blend unleaded gas.