Sulfur smell, I thinks means the cats' workin fine.

Shudder going up hill, sounds like a u-joint in the driveshaft might be going out(wouldn't hurt to grab the shaft and check for play) or maybe the driveshaft needs to be rebalanced.

The high idle and the low idle could be from a intake manifold gasket leaking and once the area around it gets warm it quits and the idle goes back down?


Something else with the idle,

Do you notice a change in it with the outside temp?