I was passing someone the other day and pushed the pedal all the way down. I got a wrench on the dash and heard a loud gush of air that sounded like it was coming from the driver side. I scanned it and got P0299. I checked all the hoses and the ebov to see if there were any holes in the diaphragm but there were none. However, when testing it for operation applying 12v, it doesn't reliably open. Sometimes it does but other times it needs just a tiny nudge and then it opens. I assume it's normally under pressure so maybe this isn't an issue. If it wasn't opening wouldn't it cause an over pressure though and not under pressure? I haven't gotten a wrench again and have used moderately heavy acceleration. I'm afraid to go full throttle again. Any ideas? Thanks!

 

You have to do better than that!
Look up the code for the official description so you know what it's about.
Turbo Boost (under) pressure performance Code.
.
Stuck Turbo Vanes.
Leak somewhere between ^Turbo and throttle Body and would include the Air Cooler piping.
Air cooler restriction.
.
Look for the leak you heard.
Something blew out!
Good luck.

 

Chat GPT can give fairly thorough explanations. It got me through a FORScan issue I was experiencing.

 

It sounds like you've got a pretty big boost leak if you can hear it... I forgot to tighten a hose clamp once - heck of a "psssshhht" sound when I hit high boost.
I'd go over all the charge pipes carefully and make sure the hose clamps are all tight and nothing has worn a hole. Check out the rubber couplers between the intercooler and charge pipes and coupling to turbos. Perhaps a hose clamp is loose enough to leak under high boost.