I have a 91 hatch with sir swap (b16a) and i was wondering if i need the first o2 sensor hooked up up .. i know i need the 2nd for vtec to work....

 

yes otherwise you'll throw codes and the thign will run like crap

 

You need to hook both of them up. Make sure you connect the right one at the right pin on the ECU.

 

you can run without any o2 sensors and your vtec will still work, vtec doesnt rely on the o2 sensor, so whoever told u that was a fucktard.

as far as your car, if you dont mind it running shitty then sure, cheap out and only run one o2 sensor,

if you want your car to run correctly then you need 2 o2 sensors, or an ecu that will cancel out the 2nd o2 sensor *(zdyne , or mugen chip)

 

I have been looking for a chip but the only place i know that just sells the chip is hyperduck tuning... you know anywhere that will just send me the chip....