Rattling sound coming from exhaust? Underneath car

[BMP99SI]

So these are my mods so far
D2 Lowering Springs
MAPerformance Street Exhaust
K&N CAI
TSP stage 1 tune
And some other exterior mods

So o have a feeling the exhaust might be getting a little loose but I’m not too familiar with mechanics. The car is definitely low and the exhaust hangs low itself, I have passed over speed bumps a lot and sometimes there’s a few that will scrape the exhaust as I pass over it. Just a little background info in case it helps. But basically this “rattling” noise comes every now and then, usually it will start after I’ve driven the car for a long period of time on the highway or after I’m done driving on a bumpy road. As I accelerate, the car will make a rattling noise. Another thing I notice is that when this happens, the exhaust seems to “burble” less. One day I was arriving home and it was making this noise so I turned off the car and turned it back on, the start up seemed weak but the rattling was gone. Any advice will help, thanks!

 

[JT Si]

You might want to lift up the rear end and check all the connection points on the exahaust pieces to see if any of them have started to loosen - a loose connection might rattle sometimes and cause an exhaust leak which might explain less burbling.

Also if you've re-used the factory exhaust hangers you might inspect them and how much play your exhaust has since they are pretty soft. I ended up upgrading almost all of my hangers to some really hard polyurethane ones when I upgraded my exhaust and it is held in place extremely well to avoid moving around and causing potential rattles or tapping against heatshields or the rear subframe.