AudiWorld Forums - I'm getting nowhere diagnosing my car. Lots of details inside.

Still fighting.... posted about this a week or so ago. Refresher, plus more info.

Car has been feeling down on power under boost for the last couple months, no obvious problems though. Felt a bit like it was pulling timing, but didn't have my vag cable to check. A month ago I blew my head gasket, was spewing white smoke. Fixed the gasket, did the N249/SAI delete at the same time. Start the car up after getting everything together, and the fun begins....

With the MAF unplugged, it idles and cruises fine, but misfires like its its job under boost. Depending on load, as little as 1-2psi (low load). Handles 5-6psi if i'm moving slow and its in a high gear, but it still has no power.

MAF plugged in, it'll barely even idle.

Mods: foam air filter, forge turbo inlet, manual boost controller, SAI delete, N249 delete, PCV delete (replaced with catch can, does not recirculate air), muffler delete (still have resonator muffler, straight piped from there). NOT chipped, or resistor'd or anything.

Codes:
4 Faults Found:

18057 - Powertrain Data Bus: Missing Message from ABS Controller
P1649 - 35-00 - -
17840 - Secondary Air Injection Solenoid Valve (N112): Open Circuit
P1432 - 35-00 - -
17695 - Boost Pressure Control Valve (N249): Open Circuit
P1287 - 35-00 - -
16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-00 - -

ABS fuse is out because I have a cut ABS sensor wire, and the ABS was going wild. Will solder wire and replace fuse when a spot opens up in my buddys garage to do it.

MAF is unplugged, already explained.

N249 is unplugged to see if it'd run any different. Vac lines were replumbed but the N249 was still in place until recently.

O2 sensor was just replaced, so I'll assume its reading correct. 'No boost' conditions put readings at .04, attempting to boost .035 down to the occasional .025, but usually .035 or .03

Coolant temp is always 90-93°C
IAT sensor is reading correct for the seasons cold outside air temps (so I wouldn't expect a fuel adjustment based off a bad reading there)

Group 116 - fuel correction is all 0%
Group 122 - timing retard reads 'no torq required' down the list

Pressure tested the system, no leaks.

Tried running on just the MAF with the MAP unplugged - not much change. (was thinking maybe the MAP was screwed up)

Not sure what I should be seeing between manifold pressure/command pressure/intercooler pressure and/or barometric pressure. I can say its commanding more than its getting, eg; manifold 1000mbar, command 1660mbar. 500-600mbar is the average difference for the entire log.

Timing- with MAF plugged in at idle, I'll get a swing of 10°BTDC to 6°ATDC. MAF unplugged, its stable. Unplugged cruising vs boosting it's somewhere around 28-30° vs 13-18° BTDC, until it starts to misfire hard, then it'll drop to 6-ish°. (Knock sensors not reading any knock at any point)

I know this is a jumble of information, but I'm trying to highlight everything I've checked across multiple logs. Everything looks normal to me, aside from the command-manifold pressure, and apparently my ECU thinks the same by the lack of codes... I'm hoping someone might be able to think of something I haven't checked, or spot something out of the ordinary that I missed.

Only other oddball thing related to my catch can. Breather filter iced up, pressurizing my block, and thats how I end up with coolant in my oil (maybe the head is a tiny bit warped?). Thought I blew the gasket again the other day, removed oil cap, pressure vented, smoke stopped. Left the breather filter off since then, no oil/water issues since.

BTW, I'll log whatever you guys think I should and post the whole thing if it'd be easier... I need to get this resolved.

TIA.