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My 17' 1.0 tsi has recently developed this issue. Normal peak boost is 1.5bar and it gradually drops to 1.3 as the revs increase.
Sometimes though i press the pedal to the floor and the car boosts to 1.0 or 1.3 bar and stays there until redline. I can feel it when it happens and the boost gauge confirms it.

It has a full exhaust, an aftermarket intercooler pipe with aftermarket BOV installed, an air intake kit and a custom tune.
The car was working perfectly with all of the above things installed. Now it has developed this issue. No check engine light or faults in the OBD scanner. Also the problem is very incosistant. It appears once every 15 or so accelerations.

Any ideas as to what can be causing this? If it was a boost leak it wouldn't do it so incosistantly, right?

I'd log the requested boost by the ecu and actual boost. If you have an opportunity to do this, that will probably tell you the issue

I suspect it could be some sort of a thermal protection.
When engine (coolant and/or oil) reaches a certain temp., ECU limits the boost to preserve engine and turbocharger.

Jay-Jay wrote: ↑Wed Sep 04, 2019 11:01 pm I suspect it could be some sort of a thermal protection.
When engine (coolant and/or oil) reaches a certain temp., ECU limits the boost to preserve engine and turbocharger.

I thought of this and checked the temps. Coolant was at 96oC and oil at 101oC.

In this case, the cause of the problem could be the BOV's spring and/or the ECU remap.
Take a look at the wastegate as well.

The first thing I'd check is the BOV imho.