On the iPad mini, ghost touching is usually related to the copper border surrounding the digitizer. this can be found on the LCD facing side of the digi. It's particularly important to cover the bottom sets of traces with Kapton tape. Higher quality replacement digi's usually have this tape already in place.
Jessa has a greta write-up [http://mendonipadrehab.com/entries/general/the-ultimate-ipad-mini-repair-post|here].
Now if all of this was done and you still have ghost touching, then you need to consider that perhaps the replacement digitizer you have is defective.