code P0430

was up everyone? My name is Juan. I have a friend that has a 98 mountaineer 5.0 with 170XXX miles. He just bought it 3 months ago. The engine is real clean. no leaks of any sort but there's a little problem. It has the check engine light on. we took it to autoZ to pull out the code and it came out to be code P0430 catalys efficiency monitor and/or exhaust system fault. does any body know what could cause this problem? Is the cat gone? we were listening to the engine run and came to the conclusion that it sounds like a small exhaust leak by the exhaust manifold at idle. Barely audible! could an exhaust leak cause this problem? Thanks for any replies!