2001 Ford Mustang Rattling underneath car during certain RP

I have a very loud rattling that sounds as if im shaking up a tin can with a bunch of loose change or rocks around. The sound is coming from underneath the car, mostly notably from the drivers side wheel well. It happens onl either during acceleration until about 3k RPMs, which then completely goes away or also once in gear at a higher RPM and I let my foot off the gas and as the RPMs fall the rattlle seems to somewhat mimic the exhaust note during the deceleration. Any ideas?