Greetings all, A while ago I wrote about a noise that my '03 XK8 made during start-up... kind of rattling noise ... from the throttle body... I suspected the throttle plate. Today, I found the issue with the help of a new symptom... exhaust smell in the cabin. I decided to inspect the EGR pipe that connects the exhaust manifold to the egr valve... sure enough it was cracke dat one of the pleats. While I am waiting for the new one, I'd like to ask the experts here a few questions; 1) Would this leak also cause the O2 sensor to read a leaner reading for that bank? 2) Would that also cause a fuel trim increase for that bank? 3) Would that explani a decrease in fuel mileage? 4) Can someone explain JUST what the egr system does and how it affects performance?
Thanks to all who reply!

I would choose to avoid trying to specify exactly how the EGR system works. Generally, it feeds exhaust gas back into the intake manifold to reduce the temp of the exhaust.

Yes, your problem could well cause the issues you describe.

Fix that, report back.

O.K and thanks, I did some research and found it actually lowers the temps of the combustion chambers on these lean burning engines. It is controlled to shut off during wide open throttle events so, it really does little to lower performance. I will repair and re-check my fuel trims and re-post later.