And exhaust leak may be caused by catalytic converter securing nuts coming loose.Google+
Car Problem Reports
Land Rover Discovery Loose Catalytic Converter Securing Nuts May Cause Exhaust Leak
Land Rover Discovery Problem
Average Mileage: 132,500 mi (110,000 mi - 155,000 mi)
Visitor, 2003 Land Rover Discovery, 110,000 mi
I also had a exhaust leak. I determined it came from the passenger side and while removing the down pipe nuts near the catalytic converter I found that one was loose, the other broke off, and the third stud and nut was not installed at the factory! I replaced everything, the manifold gaskets and the down pipe gasket.
this happened to me last week after a little offroading. one of the manifold to catconverter connection bolts completely gone. other two loose and small gap in the pipe caused it to sound like a monster truck. just got a 1/2" socket and tightened the other two back down now its whisper quiet like a new engine..piece of cake. took 2minutes once i found the problem