This is another one of those crazy projects where I spent a lot of time and effort making something I could easily buy. What can I say? I just like making stuff! In this case, I modified some inexpensive air filters to precisely fit the SU carbs on Beck TD. These filters came from AutoZone, and were suggested by Larry, who's a member of the Volvo Powered MGs online group. He said that he had used them very successfully on other projects, and the price was right at around $23 per filter, including the lower housing and pretty chrome cover.