[bluestreakgts]

I have the following mods. Not sure why it only happens when I go over 100MPH. If I blew a pipe off, then why would it be fine after I reset the light.

Jb4
AMS intercooler
Hard pipe with HKS BOV
Catless downpipes
Intake

[Rustic_potato]

Subbed, I get mine above 5k rpms, Just ordered new vaccum lines to replace before diagnoising mines

[TrollToll]

There are literally dozens of threads on this. It's always the same solution. Vacuum lines and boost leak (or DIY smoke) test. There's no magic answer.

[bluestreakgts]

I know that there are a lot of threads. My confusion is that it only happens over a certain speed. You would think that the line would blow off or something.

[cmg5461]

Originally Posted by bluestreakgts

I know that there are a lot of threads. My confusion is that it only happens over a certain speed. You would think that the line would blow off or something.

The line is under vacuum. Losing vacuum won't cause it to blow off. If your vacuum lines are under pressure, I think you have a much bigger problem :P

[limitdown]

Certain problems will become apparent only when the car is pushed past a certain limit. Your boost leak might not be massive, but when big pressure is put on it, sensors are triggered. ie the straw that breaks the camel's back.
I had a boost leak that threw codes with an aggressive tune and high boost. With a Stage 1 tune, I wouldn't get codes no matter how hard I pushed the car, .

It turned out to be a clamp at the intercooler that wasn't tight enough.

The most common cause is cracked vaccum lines. If those are ok, then do the $10 DIY smoke test.
http://www.e90post.com/forums/showthread.php?p=18793025

[TrollToll]

He's right. It's not the speed that is causing your issue. It's the fact that your car finally throws the code at that point. Mine was the same way. If you log a pull, you'll just likely find that you're under boost target for quite a while before hitting limp mode. My problem was the factory charge pipe connections. A little silicone on the O ring (throttle body end) and a new house clamp on the other end took care of it until I upgrade charge pipes. By the way, I posted that $10 smoke test. It's really simple and really effective. Search google for "30ff boost leak" and combine that with my smoke test.

[bluestreakgts]

Thanks!

[Jeff@TopGearSolutions]

It takes 3-4 seconds of underboosting to throw the code usually. (Unless it's a big leak).

By the time you get into the upper gears (around 100) you are in gear long enough for the underboost to be flagged.

It sounds like you simply have a very small leak since it doesn't do it in lower gears.

It could be old vacuum lines. I'd replace those as you can do all of them for under $20.

If your lines have over 50K miles on them, it's time and it's a 30 min job if that. Easy DIY.

If you have an aftermarket FMIC and or charge pipe, make sure the clamps are tight and the pipes and couplers are squared up.

[N44183]

Check the boost solenoids.

[blackturbo]

Originally Posted by N44183

Check the boost solenoids.

Yup this could be it as well.

[sloweste9x]

OP what did it end up being?