Loosing boost intermittently after 5000rpm

[20Vcqdriver]

Having got my 3B running right as standard, with boost around 0.7bar which is pretty much right for a 100K 3B, I fitted some mildly uprated chips (250bhp). These seem to work fine and boosted to 0.85/0.9bar. But now if you use the performance, especially in 4th/5th (6 speed fitted), the car loses power suddenly after passing 5000rpm, but NOT all the time. I thought it was because my small intercooler was overheating, but it still did it at 6.30am this morning when it was cool and damp. Performance below 5000rpm is fine with 50-70mph achieved this morning in 4th in 3.5secs. Any help appreciated!
Have looked for any previous threads on this but not found anything.

[DarrenM]

I had similar until only the other week..see link:

http://www.s2forum.com/forum/showthread.php?t=29809

[20Vcqdriver]

sort off

I had similar until only the other week..see link:

http://www.s2forum.com/forum/showthread.php?t=29809

Similar but also different. Will get codes read. Everything was by the book using VAG-COM when last tested before the chip change. I.E. the 10 values that can be monitored were spot on. Still might have to look at this water to air charge cooler sooner than expected?!

[20Vcqdriver]

more info,

Something I noticed yesterday when at full boost, the boost gauge needle is jumping. Only by half a bar max, but at a fast rate of knots. Am sure it was less with the standard chips fitted.

[Flat on my back]

.

That's 7 psi...roughly.

WGFV... Noisey signal line?

[20Vcqdriver]

Sorry I meant 0.1 bar. Slight slip there. Seems to only start happening when engine has been at full temp for 10 minutes or so. Could it be plugs?

[Flat on my back]

Jesh...

Wish they did that wiv my pay...

Might be exceeding the IAT limit...can you monitor it when this is happening, cant remember if the 3B has this feature?

[20Vcqdriver]

Wish they did that wiv my pay...

Might be exceeding the IAT limit...can you monitor it when this is happening, cant remember if the 3B has this feature?

OK what's the IAT? And how do you monitor it?

[S2central.net]

Sounds to me like chip related... Sure the 3B intercooler is smaller, but doesn't stop people running in 280bhp territory. Seems like the running problems only happen with the new chips - do they expect 2.0 or 2.5bar MAP for example ?

You can log IAT (Intake Air Temperature) with VAGCOM on a 3B, but you could measure it with some creativity - just measure resistance across it while driving and note the behaviour. Theres a graph for IAT on S2central.net which will tell you the running temp.

IAT lives on upper rear part of IM - two pins

[Flat on my back]

.

Think he's got an A6 intercooler fitted, not sure on size...

[S2central.net]

Thats a big juicy red herring... If problem exists only with these chips, then you don't need to a rocket scientist.

[20Vcqdriver]

Having removed and cleaned the IAT sensor and backed off the wastegate spring one turn (having previously wound it in 2 full turns) the fault hasn't re-ocurred. Fingers crossed!
Now just have to find where this intermittent pool of oil is coming from that only seems to appear after a hard blast!