Turbo barely spooling

[bvenz29]

MAKE: 2006 Polo GTI 9N3
KMS: 104,000
CAR USAGE: Daily
PROBLEM:

Hi guys, been having a few problems with my Polo for a while now.
Basically at the moment the car has a loud screeching noise under high throttle (I suspect a boost leak but hey I'm no expert). Additionally, the turbo does not seem to be spooling up as quickly as it used to. For example, when I first purchased the car, gentle acceleration in 2nd gear would have the turbo spooling up nicely - could hear it very prominently over the engine noise. Currently you can't hear the turbo spooling at all all the way through 2nd gear (almost to redline) but I do get the horrible screeching noise. The same is true for almost all driving situations EXCEPT putting it into 5th at say 80km/h and applying half throttle, you can hear the turbo spooling nicely. Sometimes low to medium throttle in 4th gear at medium speeds (say 70-80km/h) will have the turbo spooling nice and smooth.
FINALLY, the car seems to have a very subtle misfire at idle. Sitting at the lights the car will be idling at say 750/800RPM, then sporadically drop about 50-100 RPM and pick up again. I'm not sure if this occurs at a regular intervals. I can only describe it as an occasional stutter in the idle.

Oh and I recently had an exhaust leak fixed on the dump pipe but I suspect the guy didn't fully weld it up... looks as though there is still a gap between the welding.

Any thought on what could be wrong with my Polo? I've done a heap of research and can't find people with the same symptoms as me.
Appreciate your help guys

[seangti]

Try get your hands on a vagcom cable or someone with one who knows what to do. It allows you to scan you ECU for faults and also do data logging. That'd be your best start rather than random guessing things. Could be a split vacuum line or dodgy spark plugs or leads. But start with vagcom to scan and confirm what's going on to validate boost levels and timing, etc.

I have a cheap ebay cable and live on Brisbanes southside but am travelling for work this week and next so not much use to you.

[bvenz29]

Hi Sean. Can you let me know when you're back in Brissy? If I can't get my hands on a cable I wouldn't mind your help if you've got the time?

Cheers

[Stuwey]

FINALLY, the car seems to have a very subtle misfire at idle. Sitting at the lights the car will be idling at say 750/800RPM, then sporadically drop about 50-100 RPM and pick up again. I'm not sure if this occurs at a regular intervals. I can only describe it as an occasional stutter in the idle.

Me too! AFRs rise and fall with this too, but i can't say i've looked into it further. Keen to hear what/if you find anything.