Might have been a legal issue (BW & Garrett) than supply problems, which makes things interesting.
Some detail below, was resolved only a month and a bit ago. Whilst it's over Tit Comp wheels according to the release, could have been more there.
http://www.nasdaq.com/aspx/company-news-story.aspx?storyid=201105161453pr_news_usprx____de02971&title=borgwarner-announces-resolution-of-its-patent-lawsuit-against-honeywell
Hard to believe a foundry problem when they are 6-8 months behind, especially when only select people have received them after extensive complaints, after being told there were "none" - suddenly they got one
Perhaps there is nothing in the above, perhaps there is. Either way people are starting to specific combos all of a sudden which is a good thing.