i got the Zex Kit for my 2010. First question is, do I need to get the Zex spark plugs? Their website recommends them because they are one step colder than stock. Question two has to do with the MSD Digital Window Switch. I've read that I need to get the tach signal from the negative side of one of the injectors. Has anyone installed one of these and if so, is that where you got your tach signal?