miss fire?

[CSquared]

o2 sensors only read the A/F ratio which wont change by adding a header. But if the wiring is damaged it could think its super lean and dump way too much fuel causing a misfire.

If o2 or wiring is fubar it should theoretically throw a cel. Regarding my point, I know guys on my car when the first cat is removed will weld a deeper bung so the o2 sees less airflow and prevents an efficiency cel. That said if the head of the o2 is completely blocked from direct airflow I've got to imagine it will read lean and overcompensate causing a bumpy rich idle.

[slostang]

If o2 or wiring is fubar it should theoretically throw a cel. Regarding my point, I know guys on my car when the first cat is removed will weld a deeper bung so the o2 sees less airflow and prevents an efficiency cel. That said if the head of the o2 is completely blocked from direct airflow I've got to imagine it will read lean and overcompensate causing a bumpy rich idle.

It COULD throw a CEL but if its obd1 it may and may not. and you have a point about it being blocked. Thats possible.