2013 Ram exhaust

While under my new truck changing out the bad O2 sensor in front of the passenger side cat, I noticed how they flattened down the exhaust to put both driver and passenger 2.5 inch headpipes into a 1 inlet/2 outlet muffler with a 3 inch outlet. See pics below. That can't be good for mileage or power right. Would I see an improvement if I swapped to a 2 inlet (2.5 inch) 1 outlet (3 inch) muffler? That should improve flow quite a bit right? 2013 Ram, 5.7, auto, 2wd

Thx
roe

Yep it will, apparently worth 8 or so HP if I remember right. They've been doing that smashed y pipe since '03, can't believe they still do it