I remember a thread on this a while back but I couldn't find it using the search feature. Probably over a year old.
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In the past few years there are a lot more cars and trucks showing dual exhausts then there used to be. Back in the day if you saw a vehicle with dual exhausts it was assumed to have a higher performance engine or at least a four barrel carb as dual exhausts were supposed to reduce "back pressure" which helped engine breathing, enhancing performance. Anyone have an idea as to how many of the vehicles showing dual exhausts today actually have real duals or are most of them just using a cross over pipe that gives the appearance of duals but is not actually coming off the exhaust manifold?

Got to admit I like the look but do dual exhausts on passenger vehicles make much difference performance wise?

Depends on the entire exhaust system really. I looked at it for my tundra and true dual exhaust would reduce my low end torque. So I think, it depends….

On some cars, dual exhaust has a fake exhaust tip on one side just for the look

It was pretty funny car shopping with the wife a couple years back. She wanted a GMC SUV and we found an SLT model that had everything on it that she was looking for. The sales guy was getting absolutely giddy because she was dropping buying signals with every sentence. Then she walked around the back of the car and said "This car has only one exhaust pipe, so we aren't buying it." Fine with me, but the sales guy not so much. We found a Denali SUV at another place with its two standard exhaust pipes that we both like more. Even women like dual exhausts. Who knew?

That particular photo is of an aftermarket exhaust system. Many current cars though with dual outlets use a vacuum operated flap to close off one pipe at idle and low load conditions, and open the flap for full throttle or high load conditions. Done primarily to keep noise levels down.