You can also have your local muffler shop weld in a short piece of 3/4" pipe with a bung at the end to your test pipe and it will work the same way. If you dont want to wait.

 

Did a google search and came up with this:
http://www.audiworld.com/tech/eng114.shtml

Scroll halfway down and read up about the non-fouler procedure. I've used the longer option in the past on other cars (one on my evo when I bought it) and drilled the inside ever so slightly to allow the sensor to screw it nice without hitting the walls (note, don't need to drill the hole on the end any bigger, keep that as-is). Cheap fix (about 4-5 bucks for 2 at your local parts store) and very easy to do with basic tools.