Those plugs DO cause a problem. They're higher resistance than the spec copper core and while they will work, they eventually wear out the coils due to the higher heat loads they create. Find a spec, ohm the coils and wires to see what's what. Your description of the main problem however does sounds remarkably like unmetered air getting past the MAF. You may have an air leak in the vac system off the manifold, the more common problem of hard to find cracks deep in the bellows of the rubber elbow in between the maf and throttle plate. Or how are your brakes? are the hard and stiff? its possible to have a vac leak in the brake booster. ANYONE of those COULD cause what your describing. Lastly, what EGR system is on this car? A leak there when enabling criteria is met (car's warm) will also cause you a bad day. Do you recall anything happening right before the car got hinky? Noises etc?