I have an 03 wrx with turbo back 3" exhaust and cold air intake. I've been driving with this setup for over a year. Lately when I'm driving and it gets to about 4 grand it will start to sputter and sometimes die when I stop. It doesn't always do it and when it does i can just shut it off and then start it back up and it will run just fine. I had a buddy scan it and the only code that came up was the o2 censor, but thats been an issue since I changed the exhaust. anybody got any ideas?