Well, since i did my swap, i've had the P1446 code. As you may know, on the USDM models 03+, have the extra vsv for the gastank. I never bothered switching gastanks to remedy this problem.. Thats alot of work for 1 stupid sensor that really doesn't do much.
So finally, i got off my lazy butt and decided to make something up to rid myself of this stupid code. Its easy. Real easy. Should have done it a long time ago. I did it as follows:
1. Obtain old/new vsv, whatever your preference. Any will do, i just happened to grab one at work i had laying around. As long as its a 2 wire vacuum switching valve, it'll do.
2. I have spare wire harnesses both at work and home.. I simply found a connector that plugged into the vsv. Cut it with some extra wire.
3. This applies for my 04 wrx setup. Yours may differ.
Locate ecu connector B84. Pin #23 is the one you need. Its a red/blue wire. If you have there already, cool. If not add it. This is the wire you must add to the ecu, because its ultimately what the ecu will look for as far as something being there. Its the ground side of the vsv.
The power side of the vsv, following the wiring diagram, goes to the ecu also (pin #2 of B84), and supplies power to the other gas tank related vsv's. Although you don't need to worry about it, because its not particular to that 1 vsv. Just find a constant (IG on) power source and hook it up for your power.
4. Find your happy spot to put it.
5. Enjoy the darkness of not having the check engine light shining in your face at night.
Merely a how-to tutorial of how i defeated it.. Your experience may differ. I welcome all posts related, and how you got rid of it.