Have you by chance taken the existing DIS to an autoparts store to be tested and ensure its defective. Especially since they're kind of a pricey new, hard to locate used, and they're not on the list of commonly failing Ford parts, plus they either work or dont. If not the test is free and only takes a couple of seconds...that is as long as the parts store has the correct coupler, it took me a few tries before I found one that had the right one. The autozones around here that I tried didnt have the right connector, although Ive seen other posts which stated that theirs did. In my case Murray's did the test and it passed, which led me to CPS which was bad and saved me around 150 bucks. Obviously the cps is a little more labor but its 1/3 the price new.
If it is indeed the DIS try taking a look in the parts for sale part of the forum.