When I'm driving my 1997 Maxima SE I notice under moderately hard acceleration from 1700 to 4500 RPM I notice a strange rattling noise from the engine. I think it's loose valves but I'm not sure. Any help would be great.

Thanks

Timming chain not having enough tension. Three main problems are
Oil level
Chain tensioner or
Chain guides worn out.
Search around in the org here's is plenty information on this topic.