So the misfiring problem is due to clogged/ faulty fuel injectors so I'm getting all 6 fuel injectors changed on my Acura TL. My buddy is doing it for me. He recommends changing the upper manifold gasket as well. There's a lower which he is not changing. Should I replace both the Upper and Lower Manifold gaskets with the install of the 6 new fuel injectors?

 

Lower manifold isn't coming off which is why he's not changing the gasket. The upper gasket is made out of metal and most people just reuse it, so be thankful he's even changing that for you.

Most common problems with misfires in those cars is the coils and not the injectors, so be sure you're changing the correct part before tearing it apart.