Quote Originally Posted by Khoa View Post
Congratulate to you. All that headaches over a little oil dipstick plug, must have driven you nut.
The saga continues. The problem did get better, but its still there.

Replacing the spark plugs was surprisingly good, but didn't fix the problem.

I've spent a bunch of time making sure the PCV is sealed. Car now holds boost really well at 13.5/14 psi. Problem remains.

I replaced the MAP sensor. No change. Cleaned the MAF again, thoroughly. No change.

Then I noticed some oil leaking from the Vacuum pump, which after fixing seemed to push leaks up the chain resulting in a few clips being tightened and/or replaced. But still the problem remains.

So, I'm now convinced this is the dreaded flappy wastegate problem. Most posts I read on this issue suggest either a rattle while driving which I don't seem to have.

I've tried to send a borescope down in through the front o2 sensor but can't see anything obvious, and no movement when I try to jiggle the actuator arm.

So, in desperate need of a positive diagnosis (after throwing so many different parts at this) I tried to remove the cat but failed to convince the nuts to budge.

Reportedly, Audi's repair when under warranty was to replace the whole turbo. Apparently the wastegates flapper hinges were made with a metal that was too soft and ovals over time. The result is that the boost gauge doesn't seal properly.

I have a spare used turbo - which also has the flappy wastegate - that I'm going to try to repair with the kit from ebay https://www.ebay.com.au/itm/2-0T-VW-Audi-IHI-RHF5H-Wastegate-Rattle-Flapper-Rebuild-Kit-2009-2010-2011-2012/123471075185.
Then I'm going to pay someone to swap my turbo.
I'll post when its done to let everyone know if this fixes this most annoying of issues.

Anyone got any experience with the flapper repair kit?

My dream is to have a car that boosts properly so I can get it chipped.

Yes, I have thought about K04. I have this spare turbo, the flapper repair kit isn't expensive, and it's just a straight swap of the turbos. It will be way more expensive to get a K04, and accompanying upgrades + software.