2.8 v-6 won't fire on 2 cylinders

Hi. I have an '88 corsica with a 2.8 in it.
The problem is that I can't get spark from the coil on 2 cylinders.
I have replaced that coil tower; and the crank sensor. Still can't get spark.
My question is - does this motor have a cam position sensor that I could replace - or should I go straight to the ign. module itself?
It's on the front of the motor - difficult to see though. I wanted to try to determine if I was headed in the wrong direction before I took it apart.
Appreciate your help.
-br