Anyone familiar with 02 sensors, egr and smog pump equiptment ?

Question

4.5 liter cadallic is running rough, backfiring thru the cat/muffler after changing smog pump. itsa 1990 fleetwood

Answer 1

The vacuum control and temp sensors for the A.I.R. system are a problem. Be certain that they match the vacuum diagram on the VECI label.
Be certain that the spark plug wires are positioned on the correct plugs and position on the distributor cap. All it takes is two mis-routed to cause MAJOR performance issues.

Good Luck