i drive a 93 z28 for my daily driver and i changed the plugs about two weeks ago ran fine until about three days ago and intermittently while im driving is start mixing the cylinders and dies. it starts right back up and drives fine for another couple of days then same thing. got no clue?

 

mixing the cylinders?

 

Why did you change the plugs? I hate to bag on the opti but maybe that is going bad causing you to think its your plugs. That or check all your plug wires for arching or burns, possible loose plug boot?