My 09 TSX has been pulling to the left a bit on the highway for a while now, which can be damn annoying on my 120 mile daily commute. Last month I had an alignment done and the tires rotated but the pull is still there. Any ideas what else could be causing this? I am planning on taking it back to the shop to have the alignment checked again.

 

I remember this happening with a previous Acura...I think I went through the same steps as you. Ultimately had it road force balanced. Issue was gone after that. I'm not sure if that process is available at all shops.
Good luck, it's friggin aggravating !

 

check all your suspension components

 

Went to get alignment twice and came back with the same results. Rotated tires and problem was gone.