I have an 08 si sedan with fujita f5 Sri. DCRH. and axle back exhaust. I do have the defouler in the header for the 02. But recently I have been throwin a code stating the o2 sensor signal stuck lean. I have searched and can't really find any information on this topic. I do not remember the exact diagnostic trouble code. I was hoping someone would have some insight on this situation.

 

Have you tried a new O2 sensor? Also, I've heard that you can clean it by soaking the end in distilled vinegar for a few minutes. I'd start with tying to clean it; there's a diy on 8thcivic and go from there. These sensors are known to go bad eventually and especially if you're catless.