Nick, Hi. At 190 pounds you are too heavy for a YZ250 even BEFORE a YamaLink is installed. A YZ250 (two stroke I presume since you did not say YZ250F) comes sprung from factory for about 165 pounds. At 190 before gear and before the YamaLink you are too heavy and have too much sag.
The YamaLink extra leverage requires a heavier spring as stated on the website, the FAQ and the included instructions. On the YZ250 order page that you purchased off of it reads "CLICK HERE: IMPORTANT" and that takes you to the FAQ which covers the spring for leverage: Click HERE
Follow the instructions that came with your YamaLink: reset sag + be properly sprung. It's at the very top of the sheet right after the words BEFORE RIDING. Add 15% to 190 pounds and that is your spring rate. If in between spring rates go for the heavier rate.
Let us know if you need more assistance. Thanks!