2004 - S4 Stage 3 AMD - Weird whistle on start up when cold

[swarwi]

Hi There,

Over the past couple of weeks "the Kraken" as we call it has developed a weird whistle noise on start up, this only happens on idle when cold tap the throttle and it goes, as soon as it warms up a bit it also goes...

Any ideas what this could be?

Thanks~!