Haven't done it but just received ECS advertisement today for a new windshield cowl. Mine looks like garbage, have been thinking about replacement, and saw ECS's e-ad.
ECS Windshield Cowl: http://www.ecstuning.com/ES129793/?u...indshieldCowls
@ $47+ shipping, not bad
Seemingly helpful DIY: http://forums.bimmerforums.com/forum....php?t=1334705