Air filter Mann or K&N

about 35 mpg freeway & about 27 city/freeway daily driver '89 Jetta 4 door 1.8L originally (bored .020 over) on digi2 with a K&N air filter I'm running nothing but 91-92 octane chevron/shell gasoline.

I have had K&Ns on my last 3 diesels and 2 gas engined cars and they all ran over 300,000km. There is absolutely no evidence of fouling of the MAF, but there was a noticeable increase in power and mileage on each car and the intake track is noticeably cleaner.

I have had a K&N in a TDI for over 300,000km. NO MAF problems.

As been the pattern with the 2.5 engine, if, you install and intake and get a CEL recheck all connections making sure the 2 smaller hoses are tightly fastened and without kinks. Make sure that the MAF is properly seated in its housing.

I personally haven't had any trouble with my K&N's

on my turbo it revs a little faster.

I dropped one in and got better gas mileage, noticable power increase (slight), and a badass sound.

I had my k&n installed on my passat at 19k miles, i have had no problems but was warned when i purchased it to not put too much oil on it when you clean it as to not @!#@! up the MAF. I haven't noticed a performance gain with the K&N, however when the stock one was put back in i noticed how quiet my engine was when reving hard. I don't like it at all so im putting in another k&n(i like the noise)

I once took my maf housing out and it was really dirty... I had a K&N drop in BTW I think it flows better but it flows too much crap too.

The only effect you should notice is larger chunks of debris getting into your engine. This may cause some more noise.