Well the first filter I used lasted about 6 months until the CEL came on. That was last June when I replaced the filter - lasted about 3 months until the CEL came on again. So yeah, I wonder if something else is going on here and that eventually changing the filter won't help anymore. Something like the MAP getting flaky or other intermittent EGR issue.

FWIW when I initially did the bypass last November my mileage jumped from 27 to 30. It stayed there until the end of May when it started to jump around between 27 and 30. Could be something going on, or just because the A/C started to run constantly at about that time. Changing that filter in June had no effect on mileage, still in the 27 range all summer.

Thanks for the link. It looks very similar to what I'm using now, they don't really give out specs on the element.

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Charlie

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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)