the flex was to blame but as I have an after market exhaust they would not replace it under warrant as it hadn't "failed" as such. As it was not leaking or showing any signs of damage they were reluctant to order on in and have the warranty claim rejected. There was another fix done that eliminated it instead at my request and free of charge........they raised the idle speed for me from about 650 to 690rpm and I haven not had the rattle return in several month so far to date
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M240i LCI (Mineral Grey):- M2 Door Mirrors, M2 Black Kidney Grills, Lower grille inserts, MP Exhaust, Dinan Carbon Fibre CAI, hot climate intake elbow