From Auto Haus AZ's website:
Corteco and Micronair are divisions of The Freudenburg Group and supply a large number of filters, seals, mounts and maintenance items for most European cars.
Febi Bilstein is known for OE suspension and steering systems. From Bilstein shocks and struts to Febi bushings, tie rods and control arms, you're assured of high quality products from Febi Bilstein.
I can't seem to find anything indicating that the parts are actually made by Corteco.
I did find this:
http://electronics.become.com/febibilsteincorteco--034-cell-fltr---brand-html
It says Febi-Bilstein/Corteco.
Other than that I've no evidence.
I did see on one Passat board that Corteco stuff is apparently still made in Germany. One of the posters on there reported that Febi/Bilstein is made in china/asia somewhere.
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