Adjusting Mancini Racing Kickdown Cable/Hardware Kit

Does anyone here have experience adjusting the Mancini Racing kickdown Cable? (MRE - Kickdown Cable/Hardware Kit)

Most videos on youtube are for the Lokar type kickdown cables.

My car shifts fine at lower speeds but doesn't want to shift past 40-50 mph. It feels like I'm towing an anchor.

I followed this video, but it doesn't seem to have much detail in adjusting.