96 Lincoln problem (experts needed)

I have a 96 Lincoln Mark 8 LSC 32 valve 4.6 litre.
It started running extremely rough the other day and the check engine light
flashes constantly. There is a strong sulfuric odor in the passenger
compartment when accelerating.

I have already replaced the spark plugs to no avail.
All eight cylinders are receiving spark from the coil, however, when I
remove the wire from number 3 it didn't make any difference in the idle.
When the wire was removed from any of the other plugs, the car nearly dies.
The strange thing is that the coil IS generating spark to number 3. I have
replaced the number 3 injector and I still have the problem. Has anyone
ever experienced anything like this before. I am puzzled. Thanks!