The EGR replacement on a 1996 Cadillac DeVille with the 4.6L Northstar is very easy. The reasons that you might have to replace the EGR valve is because you may have stalling at deacceleration, rough idle, or rough running at low throttle. Instead of replacing the EGR valve, you might be able to clean it if it is sticking. The following steps are what I used to replace the EGR valve:

1.Disconnect the negative battery terminal

2.Discharge the pressure from the fuel line.

3.There is a nut that holds the fuel rail to one of the bolts of the EGR valve. You need to remove this nut.

4.Use a fuel line removal tool and disconnect the 2 fuel lines from the fuel rail.

5.Remove the 4 long bolts that are used to hold down the fuel rail and is also used for holding the engine cover in place.

6.Gently pop the fuel rail up so that you can remove the clamp from the bolt that holds the fuel rail to the EGR valve bolt. This is where you removed the nut from the EGR valve.

7.You will need to use a 10mm deep well socket to remove the two bolts from the EGR valve. Be sure to remember which bolt goes where.

8.Pull the EGR valve off of the engine.

9.There is a screw like plunger on the bottom of the EGR valve. See if this is sticking. If so, you can try to use carburetor cleaner to try to clean the carbon out .

10.To put the EGR valve back on, just do the reverse. You may need to replace the gasket if it tore during removal.

This is a relatively easy replacement and if you have to buy another EGR valve, you will be looking at around $200 for the part. So, if you can do this yourself, you are going to save yourself about $100 in labor charges.