General LSX Automobile Discussion - noob question on 02 sensor location

ok. so a ls1 has 4 02 sensors stock right? when two are removed its typically the back ones right? or is it the front ones? i'm looking at my car and i dont see any 02's at all :eek2: the tuner i'm talking to is an old school street tuner and says the car has to have 02's.. now, with my 240, i got it tuned on a closed loop? or open. i get the two mixed up (the one that you dont run 02 sensors) but that was a turbo 2.0 4 cylender. a little different to a 5.7 v8 lol. so what i'm asking is where are the 02 locations on the car? i see the two bungholes coming off my long tube headers, but they are blocked off.

if it matters, i have jtr long tube headers, off road y pipe, to a custom made exhaust. any help would be great since the tuner said he wont touch it if it doesnt have any 02's...

the ecu was "Serviced" they "removed VATS, two o2's... little stuff" so i guess the ecu has been tuned previously. now, the car i have it in is motor swapped. it's in a mazda rx7. idk if that matters or not. not the fact that its in a mazda, but that its a swapped motor in a car that never had a lsx in it.

Rear o2 are common delete i have 3 sets if u need some but basically they let ecm know converters are working

Front o2 are in the headers rears are in the y pipe sorry i missed that part of post lol

in that case, i'm almost positive i dont have any o2's... great. how is this? the car ran fine before. i cant get it to idle now with the new heads, intake manifold, bigger tb and cam in it. but its also untuned... ugh. idk.

because wouldnt the car have issues running without any way for the ecu to monitor this?

ok. found one of the o2 sensor pig tails from the harness. so i assume the driver's side is there too. so i guess all i need is to buy a pair of 02 sensors? any recommendations on what i should buy? prefer something i can buy in person as apposed to buying online.