I have one on my truck. Its a NTZ G26
I picked it up off of ebay along with 2 dozen replacement cartridges for about $100
Ive only done one uoa since Ive had it on the truck and it was making a difference. I'm going to be having another UOA done here soon and I will post it.
Overall its a nice unit and I'm happy with it. Ive seen some of the newer ones on ebay and there not cheap. I tried looking up more info on them and pricing replacement elements but didn't come up with much.