Any reason prior owner would put a performance muffler on a 4DR 4X4 Limited Explorer? It's much louder than a standard muffler?Should I take it in and get it replaced?

some of those "performance mufflers" are cheaper to replace than stock units, that is one explaination, the other is the old owner like the sound. As for the shocks they were more than likely cheaper to replace than stock units or there was a sale or the old owner had a preferance for them. Hope this helps, best of luck.

Agreed, stranger things have happened. We saw a 2-year old Dodge Caravan come in to the dealership which someone had just purchased. He asked us about exhaust noise, and when the guys checked it out, here the previous owner had put a "performance" muffler on the minivan. The van wasn't even old enough or had enough miles for the OEM stainless-blend muffler and pipes to have failed, so he had to have spent some bucks to have this done on purpose. The new owner asked us to replace it with stock parts. No rational reason why people do the stuff they do sometimes.

If the engine is a V-8 it probably sounds pretty good. If it's a V-6 it probably sounds, well... stupid. Sorry. And the after-market shocks are likely to help keep the rear of the truck level with the front. When our stock shocks were getting worn out the back of the truck sagged noticeably, & overly so when towing a trailer.