Mine seemed a bit different than other threads on this I have read.

Self HP tuned on stock 2009 with just a KN drop in filter. Seem to run strong and perfect in every other way than this. Was GMS1 before I started tuning.

Been running into this issue only after I run through one gear and partially into a second boosted gear. will get a P0299 code pretty consistently. But never when I am just going through one gear. I can make it through a 4th gear pull of 7.5 seconds without it happening. But a quick 2nd gear pull, and then into 3rd, the code will happen at about 5.5 seconds total boosted time, and only about 5500 rpm into 3rd.

On all boosted pulls boost holds exactly as it has since I started tuning, 22-23 psi, fading to 20-21psi at redline of 6300. never any problem keeping that boost even on long single 4th gear pulls.

Attached is a screen shot of the HP log with the marker just a fraction of a second before it went into limp mode. I did not lift out, until after the PCM cut the throttle on me.

Everything to me looks good in the logs and I don't see any reason it would trigger that code. I know it is often mechanical and a boost leak, but AFR is on target and trims are good, so I don't think it is of a boost leak nature (should see trims get out of wack as it tries to maintain AFR but it does not).

Car otherwise seems to run perfect and strong (all stock parts btw).

Let me know your thoughts if the tune could be involved, or an electrical solenoid maybe giving out and not holding (wastegate or BPV solenoids?)


TIA