Customer has a 90 seville with the 4.5. the car is dying at red lights and while slowing down from highway speed. there are no ecm codes in the computer. I did notice that the spark degree was changing quite rapidly right before it would die.

Dirty throttle body? Bad or dirty EGR valve or solenoid?

ok pulled the throttle body. lots of carbon on the butterfly valves. lots in the bottom of the intake.