So according to my friend who was behind me on the freeway, my left muffler shakes a bit. I have aftermarket Apex'i catback.

Basically, my muffler shop guy welded the exhaust on so it wouldn't have the shaking. I plan on following my car one of these days to check it out.

But should I be worried? If both mufflers had an equal amount of wiggling I guess it would be fine, but my friend only stated the left one was doing it.