1988 Oldsmobile Cutlass misfire and stalling

I have changed the fuel filter, pump, and ignition wires. But my 88 olds cutlass cierra international wagon is still having misfire and stalling issues. The misfire is intermittent and happens more when accelerating. But it can happen at any time even at idle. When restarting the car at times the car will start then die again. It runs rough when it does this. After gunning it it seems to clear up the rough running but there is a lot of smoke and the smell is bad. It does not smell like oil burning more like sulphur smell or egr. I had the code read and came up with EGR failure but egr valve seems to be working fine and when I disconnect the vacuum to the valve it still has the missing and stalling. I am kind of stumped and out of ideas at this point. Aside from replacing everything I thought I would seek others wisdom first. Thanks for any help you can give.