EkSiPd

Ok so this a bit of long story...as a forewarning.

First of all I'm running GIAC X flashed. Originally i had a bad N75B valve, only 10-11psi in chipped mode, no boost leaks at the time. So at that point i swapped for some valves that my friend had for his GTI. N75H and K. Both saw perfect amounts of boost spike to 16-17 with normal taper from there, significantly stronger pulling car. So i ran the N75H and K for a while now, lets say 15-20k miles. I hit 80k miles, got a code that my driver side O2 was going out. Ok replace those recently. Pull them out to find that they are fairly white and chalky...

<a href="http://s100.photobucket.com/albums/m21/EkSiPd/Audi%20stuff/?action=view&current=Picture.jpg" target="_blank"><img src="http://i100.photobucket.com/albums/m21/EkSiPd/Audi%20stuff/Picture.jpg" border="0" alt="Bad O2s"></a>

so i assume I've been running lean for a while, however I've never gotten any codes to indicate as such. (Although i do not have my own VAG tool, so i don't log as frequently to check. Last check was a few months ago while i was running the K)

So despite boost being fine, i finally break down to buy a new N75B oem valve. Throw that in. Disconnect battery for the night. Start it up the next day and first thing i know idle feels a bit smoother(placebo?) Gas mileage is back up. (Both O2 replacement related, noticed with all 3 valves) Car used to have a stumble on very light throttle around 3k like others have described as a hiccup or whatever, which is almost completely gone with new N75B. However boosting is erratic and car feels slow in in higher gears. Hammer down at 3-3.5k in 3rd-6th only nets 13psi. Let off the gas briefly and throttle down again ok now it holds 14 or 15psi. The only time it spikes and tapers is going between shifts. ie, Wind out a gear, shift, throttle on, boost hits 17, instantly falls to 13-14ish and holds tapering to 11-12 by reline. Put the chip into stock mode and I'm only hitting 7psi, same characteristics. Shift and back on throttle and it spikes to 9-10 instantly holds only 6-7psi till redline. H or K would easily hold 9-10psi in stock mode and taper to 7 by redline.

Boost with H or K held better under stock and chipped modes.

Could it be i bought a brand new Oem valve still in the oem packaging that is bad? I haven't adjusted the valve or anything and its position is parallel with the firewall. I doubt that there is a leak, if i am able to hold normal boost with the other valves, and no rise and fall characteristics. I checked all the problem areas for tears, holes, etc. Replaced BPV's. The lean looking O2's would suggest I'm overboosting possibly, but no codes. What should be my next step? I know everyone is gonna say i need to pick up my own VAG tool to do some more in depth logging. I'm working on that. Wondering if there are other places i should be looking? WWAWD? Please help! TIA.

DVS27t

If you drove the car at WOT 100% of the time and they looked like that it would be a different story...

SoSlow

we need to see a log of actual vs specified, log 115 - your new n75 might be bad too

EkSiPd

really wanted to see if anyone had any clue as to what might be going on.

I will be shocked if the brand new still sealed in a bag N75B is bad. But who knows.

SoSlow

wouldnt be the first time a new n75 was bad

nyet

pointless to guess w/o logging

ErikS4

(and luckily inexpensive) boost pressure sensor. It's the sensor on the TBB. You could try replacing it - and I have no idea how to log it to find out if it's the problem before replacing it.