How to set the 2M PHY Mode while searching for a Bluetooth device? https://punchthrough.com/crash-course-in-2m-bluetooth-low-energy-phy/ is there any interface method in CBCentralManager to set these flags?

We have observed a significant increase in download time from the sensors to the mobile device after recent OS updates. We are connected to the external sensors via the BLE interface using the following connection parameters(15,15,0,6000) https://mbientlab.com/tutorials/MetaMotionRL.html: example 1.For 1 Meter with duration of 28 Seconds the IOS 17.1 taking 44 secs where as IOS 17.5.1 taking 82 secs . 2..For 1 Meter with duration of 45 Seconds the IOS 17.1 taking 74 secs where as IOS 17.5.1 taking 143 secs . Even with the same connection parameters, download times were considerably lower in iOS 15 and below devices. We are currently using the connection parameters 15, 15, 0, 6000. I have learned from some documents that the minimum connection interval was changed to 20, but when I tried it, the download time increased further. I am seeking assistance on how to achieve the same download times as the older versions. https://mbientlab.com/community/discussion/comment/11852#Comment_11852