Hi there
This code is for the front sensor and yes, if you take it out of the exhaust stream it's going to set a code for slow response. This sensor should be in the exhaust ahead of the converter and no spacer should be needed.
P1279 NISSAN - Air Fuel Ratio Sensor 1 Bank 1 Circuit Slow Response Read more: https://www.autocodes.com/p1279_nissan.html
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