After putting a Perrin exhaust system on my 2008 STI - including up-pipe, down pipe, and quad tip catback, the CEL has been on. The CEL is solid when the car is turned on, along with a solid traction control light, blinking cruise control light, and blinking S (Sport) mode light. The only other modification is a turbo timer, and blow off valve which were installed prior, and did not cause any problems with the CEL light. The code from the CEL is P0183. Even after clearing the CEL, once the car is restarted it comes on after about 5 seconds. I also have the Cobb tune for Stage 2 installed for CA,NV, and AZ. Any suggestions as to what to try to make the CEL turn off would be great.