For a long time I've been battling an overboost and rough pickup issue on my 1.9 16v. I had the EGR blocked off for a long time which seemed to help but I still always got an Overboost error when putting the foot down in 5th or 6th gear @ 3k RPM.
I even started a thread on this a long time ago:
So, the other day I came across this:
Alfa Romeo forum: Cleaning JTD turbo with Mr Muscle
This morning I decided to give it a go. Procedure was as per the link,
Remove the U shaped Airpipe, remove the top heatshield and undo the Hex nuts holding the EGR. Then I loosed the clip to bend the EGR pipe out of the way. All this took 15 mins.
Then I got a bit of window washer pipe from halfords and a can of Mr Muscle Oven Cleaner. I used a small cable tie to attach the pipe to the top of Mr Muscle. Again, as per the post in the link above, feed the other end of the pipe into the EGR hole and down into the turbo. As the previous post says, make sure the hose is going to the turbo and not the exhaust manifold and thus the head. You'll need to stick your finger in there to make sure you you'll know when you have it right. It's a definite right angle.
Squirt in the Mr Muscle and leave for 2 hours. You can put everything back together in this time.
Then its a case of taking the car for an easy spin to warm it up and then blasting it down the motorway to burn off anything that's left behind.
I could not get the car to throw the error. I have a boost gauge fitted and could immediately see the needle is far more "lively" and responsive and does not boost higher that 1.5bar (used to hit 1.7 ish before limp mode kicked in). The car is pulling like a train, pick is improved and acceleration is smooth. It feels like the car has shed 150,000 miles in 2 hours (It has 237,000 miles on the clock!)
I'd highly recommend this easy fix if you suspect overboosting due to a stuck vane in the turbo.
Before doing this, I had made sure I had vacuum from the reservoir, that the VNT control was working and that the actuator was OK. I'd checked the MAP values too. Basically I had removed the chance of any other components being at fault. Also worth noting that the actuator WAS moving freely on my car before performing the clear. In my opinion, just because its moving does not mean everything is moving as it should inside.