The cheapest L1H1 O2 sensor for VX that I could find a couple months ago was from quality_auto_parts:
http://myworld.ebay.com/ebaymotors/q..._auto_parts298
He's selling them for $178 incl. shipping. I bought it and it fixed hesitation and high fuel consumption in my VX. Now it's getting over 50mpg.
Supply of L1H1 wide-band sensors is very limited and there is a strong demand for them to use for engine tuning, so I don't think it's possible to find them for less than 150.
Sensors that sell for $50-80 on e-bay will throw CEL. It's been confirmed many times. They are for a different vehicle (Audi) and calibrated differently.
I'd go with knock-offs if the only other option was to pay $450 list price to the dealer. But with genuine wide band sensors available for under $200 I would not recommend getting substitutes.
Ross
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