Just installed Z110 in my 2009 VW Jetta Sportwagen. I used the Connect2 harness to connect to the CAN bus and retain steering wheel buttons. I had read on a VW forum that it retains the functionality exactly as stock, except adding the OK button becomes change source (which it does and that's nice). The problem is that the up/down arrows on the right changed the presets with the stock HU and now they are doing tune up/down. On the VW forum someone said it is a Pioneer issue. I am doubtful. I had actually bought all of the PAC stuff to use and may end up using it if I can't resolve this otherwise (plus I might be able to use the Phone button to at least answer calls whereas right now it does nothing, same as stock)... One reason I went with Connects2 instead of PAC is it is much simpler(one translation box and harness vs three) and less expensive and smaller/easier to fit behind the Z. No programming is required or possible (good and bad)...

this is a long shot but maybe something that can be changed with the vag com?

I think I would have to use the PAC stuff to change it. The Connects2 does change track when you push and seek when you hold the up/down buttons. I had a Z1 in another vehicle and with the PAC stuff setup that way it would do what the Z110 is doing, ie tune up/down.