i have a hi flow cat that i was gonna put in my obd2 97 teg gs. only problem is there is not a spot for the o2 sensor. what will happen if i dont use the o2 sensor?

 

if you don't install the secondary O2 sensor and you retain the OBDII ecu, then you will get the check engine light and one of several different codes.
Don't plug it in...get a code of P0141-heater failure.
plug it in but don't install it into the exhaust stream...you will get a code of P0420..converter failure <won't set right away-it will take a while>

neither of these will have any noticable effect of performance.

 

im switching to a p73 ecu so i guess ill have to tap a hole in the cat for an o2 or deal with the check engine...thanks for the info