Hi,
I have had a 92 excel for several years now, and it has been totally
trouble free untill today.

I noticed it running very rough, and have determined that it has
suddenly stopped fireing on the leftmost two cyclinders.

I checked the plugs, and found them to be clean and dry with no fouling
evident... Just to be safe, i replaced all 4 spark plugs, roter, cap
and ignition leads.

A compression test reveals that compression is normal in all 4
cylinders

What are the types of things that can cause this, and what else can i
check without pulling the motor apart ?

Could it be a problem with the EFI ?

regards,
Michael