It depends who you talk to. Some people say tune it like you would gas, and some say go leaner. I have read quite a bit on the subject (including other boost forums like evos, supras, turbo neons) and my conclusion is the tune is going to be happiest around 11.4, which will still be plenty rich as some tune to around 13 without issues. We all know that every car is a little different though so there is no 1 magic number.
edit: I should mention that I'm thinking closer to 30#'s with my above statements. At 20#'s 11.5 AFR should not be an issue.
Interesting. I'll try it once I"m comfortable with this initial tuning we're doing. Why so much leaner at 30lbs, if you meant 13 AFR?