it started a few days ago. i got error code p0171, fuel mixture running to lean in bank one. i cleared it and a few days went by before i saw it again. i cleared it again and added lucas oil fuel injector cleaner.then i came back sooner and sooner. I cleaned the MAF with CRC MAF Cleaner. Reassembled and light came on again soon after. I figured maybe a vacuum leak although my boost/vacuum gauge reads at 20-24 in. hg. so from at least where we hooked it up at the vacuum line off the intake manifold to the fuel pressure regulator. Id say the MAF although according to my bently manual it should run between 2.00-4.5 GR/SE at idle. I had it at 763RPMs my MAF read 2.75 GR/SE IAT was 113 F
at 2083 RPMs MAF read 1.75 G/SE IAT of 102F
at 1791 RPMs MAF read 21.0 GR/SE IAT of 100F
those were just a few select frames on my scanner. i also changed my fuel filter, air filter is a K+N n a stock arm. my motor doesnt seem to drag down or run crappy seems same as always. if its a fuel injector problem is there anyway to test. there 10 a peice on mjm autohaus.. i already droped a few grans in to my timing, and suspension.. im outa dough any help is well appriciated.

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01 audi tt, awp fwd. ive never learned as much about anything.. before i got an audi.. problem proven. but fun to drive.. no one respects a ford.. every one respects an audi (=

update: today i started my car and it bogged out bag, didnt get the MIL. although i did a v-scanner check and got a cylinder 1 + 4 misfire and recirculation valve failure. i upgraded my diverter valve after that. but im still running lean and the intake seems to have a bit of oil in it. the stock diverter valve had oi on the lip, and mst of the hoses had ol in them. like the one on the valve cover (which kind of makes sence). although im not sure if oil in the intake is a god thing. ive heard it could be the PCV valve. maybe egr?? anyhelp is appriciated. would oil in the intake cause a miss fire, and running lean? my ngk plugs arnt too old. and i got new coil packs from napa. i think there echlin brand, says made in germany so maybe oem replace ments not third party, but i think bosch makes original.

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01 audi tt, awp fwd. ive never learned as much about anything.. before i got an audi.. problem proven. but fun to drive.. no one respects a ford.. every one respects an audi (=

Well the code you got is for an o2 sensor i believe. Maybe you should start there?

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TT 225 Silver/Black
Red calipers, Forge Black 007p, n75j, Autometer Pro-Comp UL Boost Gauge, 18x8's, Neuspeed Sports with Koni Yellows :-)

most causes are PCV realted-
PCV is going out also that big hocky puck black pressure valve(kinda looks like a big DV) can go bad. EGR really shouldnt be involved on this one...but hey u can get rid of it. can also get rid of PCV but i dont recommend it really. the PCV system is a lot of hoses and suction valves and more valves and housings...etc

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09 135i montego blue 6speed...RR catch can,CDV, then to do something about the amber reflectors "save the cheerleader save the world" we all wish we could be heros..... sold my beloved 2001 Audi TT225hp tastefully modded