exhaust leak?

[nisssan-drive]

ok I just got a rebuild and now there is two strange noises coming from my car. One is from the back end of the exhaust (sounds kinda like metal clinging together) I got under there and I couldn't figure out anything. The other is from the engine after I let it idle for about 30 secs, the noise from the engine is hard to explain but I let the guy who rebuilt the engine hear it and he said it sounds like an exhaust leak. also some times when I put my car in nuetral and come to a complete stop the rpms drop to about 500 and it feels like its going to die.

Any help would be appreciated Thanks.