I didn't know that last of the old 45cc models came with a cat. Interesting.
Husky changes cat mufflers off and on through the years, seemingly without reason. For example, I have a 45cc 346 made in 2005 with no cat. I am using a 346 NE that came with a cat/green gas cap that was produced in 2006. I have seen two recent 346 NE's from 2009 production with no cat/green gas cap sitting on dealer shelves. Hmmm.
Yes, I can't figure out the ryme or reason to cat or noncat either. I recently purchased a NE produced in 2009 with no cat. That one OE produced in 2006 is the only OE's that I've seen with a cat muffler. Maybe that makes sense a little where your 2006 NE came with a cat muffler. During the switch in 2006 from OE to NE at some point both were getting cat mufflers.