I am working on turbo-ing my Echo. One issue I was facing was deciding how to extend the MAF wires to the location on the intake tract I am planning to place it. I really did not want to cut the original harness and splice/solder wires. As such, I did some research online and found an extension harness on Ebay for 5-pin Denso MAF's. The seller indicates that it works with other vehicles, including the Toyota Tacoma. After inspecting some pictures of the Tacoma MAF online and looking at my own, I decided to give it a shot. It works from what I can tell. If anyone is interested, please see this
link.
I believe Yarii share the same 5-pin connection, so I think it should work, though it would be helpful if someone with a newer Yaris experimented with this as well.