Engine management light on with p0170 powertrain fuel trim (bank 1) on the diagnostics. Lumpy like theres no turbo kicking in when she's cold and very loud in the engine bay almost like a blowing exhaust then shuts up after 20-30 seconds. I know there must be a vac leak but where from?

Sounds like you have a leak on the secondary air intake.

Try unplugging the MAF sensor as P0170 can be caused by it dying. If the car runs better without the MAF that's your problem. Replace with a genuine VAG part only, & not a cheap aftermarket part.

The exhaust like noise on cold start will be the SAI leaking. Usual cause of this is the rivets holding the SAI housing together failing, which is an easy fix. Drill out the rivets & replace with nuts & bolts.

Thanks lads, will give this a go, is there any "how to's" on fixing the SAI?

http://uk-mkivs.net/forums/p/141240/940861.aspx#940861

Legand! Will get this sorted on the weekend, forums really do work

Not fixed, not getting as much jumping but now when it hits the turbo range it whistles like hell. And down on power. Only cleaned the MAF so far but redone the sai pump. And engine management came back on.

My sai pump has broke free of its mounts and just hangs inside its round bracket

Sent from my iPhone 4s

Mines all bolted in and rivets replaced with bolts but the recirculating pipe to the air box just won't clip in. Could this be the the problem? Anyone know?

The corrugated SAI pipes have squeeze clips which are very easy to clip in & out if you know that, but a lot people break them not realising how they work. If you have a pipe off that will be a problem.

My sai is held on by cable ties lol

Sent from my dad's old HTC Incredible S, not a dodgy s3!

Have tried everything but a real arse to got too when its all back together. I think it must be the problem as I've managed to get it kind of on there and it's temporarily stopped but if gently pulled it just pops off. I hear replacements of these are expensive, has anyone ever replaced them with silicon pipes? Will this be the cause of the whisling under boost?