Please consider many factors will affect the wireless iPerf results such as RSSI/SNR/Frequency bands and channel widths.
If running the iPerf Test via the Test Accessory also see General: iPerf & Speedtest Limitations
NB: If the Air Quality Test is ran after the AutoTest it will break the link to the network and you will see the error “The selected port is not linked (17)” when trying to run the iPerf Test, to resolve this, re-run the AutoTest