Just wanted to give a quick update for everyone. I managed to find some old threads where fluctuating boost was an issue and cleaning out the wastegate solved it. This was apparently my problem all along. I checked the wastegate arm and it mooved smooth and freely, but the wastegate itself had a bunch of oil buildup. The nipple was just big enough for a plastic spray tube, and I filled it up with brake cleaner three times and blew it out with compressed air in between. Burpod is still helping me out with a custom tune because the Malone Stg 3 isn't mapped very well, but thankfully the overboost code seems to be tied strictly to a dirty wastegate actuator.
Four months later, still no 00575 codes. I'm dealing with a bunch of boost spikes/dips again and wanted to document it somewhere. This is what it looks like when logged and plotted:
It's hard to keep a good memory of how things used to look when you have a problem like this that comes on slowly. I tried a few different ECU tunes and none of them really changed anything. I unplugged the boost hose connected to the wastegate actuator for testing purposes, and the spikes stopped altogether although it obviously overboosted quite a bit.
This morning I swapped out my relatively new Pierberg N75 with an old VW/Audi N75 I had stored back. Although the spiking isn't completely gone it's mostly smooth now at lower speed/torque.
I have a theory for the higher-torque spiking that occurs. My clutch is slipping pretty badly at the moment. Perhaps the spikes I'm seeing are correlated with minor clutch slips, as shown in my high-tech diagram:
At least, that's the only thing I've got right now. I might replace some of my vaccum lines as well. Either way I'll be installing a new, higher-torque clutch ASAP.
