DG wroteMakozak, you need to check your line stats, more specifically the modem uptime along with the number of CRC, HEC and FEC errors while Interleaved is ON. This will help you decide if it's worth turning Interleaved OFF.
It's worth nothing that you will only get FEC errors when Interleaved is turned ON. FEC stands for "Forward Error Correction" which means most packets that have errors can be corrected at the receiving end without the need for them to be re-transmitted.
Most of these FEC errors will become CRC and HEC errors when Interleaved is turned OFF. So if you have a lot of FEC errors to start with, I'd be cautious about turning Interleaved OFF.
I don't think having Interleaved ON or OFF makes a noticeable difference in connection speed unless you have a lot of errors which will mean the unsuccessful packets will have to be re-transmitted once you are on FAST PATH (aka Interleaved OFF).
How much you think is on ok number on FEC CRC and HEC to consider going fast-path?