Ok, I had the same
problem and I changed them all (both exhaust and intake)
Here is the information :
Technical Service Bulletin
Re: K04 2.0L TFSI Top End Misfire – Valve Spring Float
Vehicles Affected - 2008+ K04 TFSI engines found in the
Audi S3, Audi TTS, VW Golf Edition30/Pirelli Ed, SEAT Leon
Cupra.
The official diagnosis from the manufacturer is that due to a change in
production of the exhaust valve springs in the 2008+ K04 based TFSI
engines; certain vehicles can suffer from a misfire whilst under load at
the top end of the rev range (over 5500rpm) caused by valve spring
float. Not all 2008+ K04 vehicles will suffer from this
problem, and
some will be eligible for warranty work to rectify the
problem. Revo
have a revised stage1 .RVO available to limit the misfire over 6000rpm
for those customers whose cars are not eligible for warranty
replacements.
Valve Spring Float: a condition that typically occurs at higher rpm when the
valve lifters don’t remain in contact with the camshaft lobe, caused by the valve
spring being unable to effectively control the valve.
Although this issue can be seen on standard cars it is more likely to occur when
running higher boost levels than 1bar over 6k rpm. A misfire occurs and a fault
registers (normally on Cylinder 3). The
problem being caused by weak valve
springs. These are only seen in the 2008+ engines/replacement parts and seem
to have been rectified in the late 2009 onwards vehicles. Currently there is an
Audi TSB out in regards to this issue and main dealers have been known to
replace exhaust valve springs on cars that are affected.
Note: Lowering the boost level or fitting a higher flowing exhaust system reduces
the symptoms.
If this issue occurs on customer cars then there is a possibility of the
exhaust valve springs being replaced under VAG warranty. However Revo
have available revised .RVO files for these vehicles that counter the issue if
required.
This issue is not to be mistaken by misfires caused by weak coils, plugs or faulty injectors.