Do later model rx7\'s have two O2 sensors?

[Panjy]

Just bought a 96 model fd3s rz. Been fiddling under the bonnet this week and in doing so noticed some wires that looked abit out of place. Traced them to a tomei air flow amp (gauge has been removed) under the passenger footwell carpet connected to my ecu and a second O2 sensor on my feed downpipe which has four (not the usual one) wires coming from it.
 
From looking in the online manual (for 93 spec cars) only one O2 sensor is shown. Did the later cars have two or has mine been modified and hence i can remove and bung the 2nd sensor on the downpipe and tidy my engine bay a little?
 
Any advice appreciated

[1990_fc3s_t2]

Is it a wideband 02 sensor? Do you have an afr gauge?

[Panjy]

I have no experience of wideband o2 sensors (other than hearing about them) but guess that as this one has 4 wires coming from it and the other sensor in the original position has only the one then it must be for diagnostic/tuning purposes.
I did some searching on the net last night and what i have is definately a tomei air/fuel ratio kit (minus the gauge).
It seems to have just been spliced in to one of the wires entering the ecu so i\'m guessing it can simply be removed and the sensor position in the downpipe plugged.
Just want to be sure before i potentially upset my cars engine management.

[Panjy]

Surely someone with a 96 or later rx must know the answer to this?