...don't buy 'em.
I bought my Boss' passat TDi 115BHp (woo, yeah, exciting..) for a song back before new year, 'cos it wasn't running particularly well - wierd throttle response, lacking power. He reckoned it was fooked, but I thought it was probably a duff MAF, so I got a cheapy one off ebay for a few quid to try - there was a huge improvement, so I was chuffed and drove it for a few '000 miles. There was still a slight hesitancy at part throttle and economy wasn't *great* (~42mpg), but I put it down to my driving style and it having been remapped. Last week, on a whim, I rang the local motor factor to see how much a proper Bosch MAF sensor would be (£60 exchange), so I got one and fitted it. Throttle response is much more linear, the hesitancy is gone, sooting is much reduced and on a few hundred mile hoon around the lowlands of scotland with bike rack and full load I got ~50mpg. I'm pretty chuffed. Of course it's still a B5 passat, so not the most dynamic thing you'll ever find, but the point is don't bother saving £25 by getting a cheapo ebay MAF - I'd have made up the difference in about 3 tankfuls...