I just got my 08 WRX about a month ago. It has STP exhaust and a Cobb DP and I have no idea if it has a good tune. I am thinking probably not.... First thing I bought was the Tactrix unit so I could do some datalogging. I also installed an AEM Uego. The car has been running fine since I bought it. However, yesterday at idle the AFR would randomly go from running very rich to very lean. As in, almost maxing out the gauge in each direction. When I would go to accelerate from idle, it would hesitate and run a bit rough until around 1500 rpms and then smooth right out. Also, driving parking lot speeds in say first gear when it showed the AFR to be very rich, there would be a backfire type noise coming out of the exhaust when I would get off the throttle. Any ideas as to where I should start my investigation would be much appreciated.
Today though, it has seemed to smooth out with the AFR readings.