I am having issues with my 03 WRX, I wasn't getting any boost. I brought it into the shop and they replaced the Air/Fuel ratio sensor. It was stuck at 3.7 volts. This didn't fix the issue, so they suggested that because this sensor was off that it messed with my cat in the up pipe. So I purchased a catless up pipe and replaced it yesterday. Taking off the old one, the cat was shot. So I know this was an issue. But it still didn't fix anything. I am still getting no boost. And whenever I go to completely stop and idle it stalls. Does anyone have any suggestions of what to do next??