The brake master cylinder is very likely not being allowed to achieve a full state of release, which seems to be a problem we are seeing more and more of lately with vacuum booster / aftermarket MC's (especially when spacer bullet / plug design MC's come into play).
Here are some links that will help get you squared away:
http://www.pro-touring.com/showthrea...Brake-Problems
https://lateral-g.net/forums/showthread.php4?t=17060
Do please remember to report back to let everybody know what you find, so that others can be prepared and learn from these scenarios in the future.
