I hope the adapter you ordered from ECS Tuning was the correct part! I think they have one for the LCI mtech which looks different from the Pre LCI mtech. Although some say that the LCI mtech doesn't require any adapters and it's supposed to be a bolt on fitment to the pre lci e90s, there is still a "belly pan" adapter for it. Make sure you got the right one!
On another note, thanks for the referral on extremeparts.ca. Is the bumper made from polypropylene or polyurethane? Have you tried fitting the lip to the bumper yet? If so, how is the fitment? Are there any gaps whatsoever? I have the lip as well and couldn't agree more on the look. Let me know on how the entire process goes and how everything fits together. Looking forward to see some pics of the final result! I may very well buy it from the same vendor.