OK i've been having problems for a while with smog (from the BAR). I pass 25mph test and fail bad on the 15mph (HC and NOX are double max) I'll post the actual numbers later when I have them with me. So any way i've change the cat with everything except a new stock cat. I've also change to O2 sensor and i've used sea foam. I've also checked the timing and exhaust leaks. So I need to know what could be the problem and how I can check to see if it is the problem. Any help would be greatly appreciated.

I have a 95 civic with B18b swap, headers, intake, and larger exhaust piping.