Sorry Ive never been on here before but I hope this helps someone.
I have a pair of BMW 335i Twin turbos off and on the bench here and I think I can explain exactly whats going on.
100% Standard 2007 '07' BMW 335i M Sport Saloon Auto, 1 Owner, 49,000 miles, Full BMW Main Dealer Supplied and Maintained
I have a video which I will upload so that you can see the extent of the problem. Once you have seen this video ask yourself who should be paying for this problem and let me know.
The full extent of the problem is as follows;
You can here rattleing from what sounds like the wastegate actuator arms and sometimes a tinkling as you come off the throttle similar to the sound of a turbine blade? (You don't always get the tinkling).
The wastegate rod as it comes of the actuator has some play at the joint where it meets the wastegate arm that goes through the body of the turbo connected too and activating the wastegate open & close.
BMW have a PUMA with a solution which is to add a small part to the joint basically taking up the slack & cure the rattle (Possibly a new joint Iam not 100% sure, However!!
Now the turbos are off we can see the full extent of the problem.
Yes the joint is poor, its elongated where the pin joins the two pieces together, but grab a hold of the arm end where it goes through the body of the turbo and the worn freeplay through that bush is astounding, that too has elongated and is rattleing around. Then look inside the exhaust exit where the wastegate valve cap is and even the wastegate is rattleing around, you can see the polished mark where the valve seats, however they are so badly worn that the polished mark where they close is only polished half way round the seat, its because there not fully closing!! (this sometime causes a 30FF fault code, low boost pressure & possibly restricted performance although sometimes intermitently).
Basically what your all experiencing is turbos that are worn out on the exit wastegate side of each of the two turbos. The combined slack from the actuator arm linkage through the wastegate arm bush in the turbo body to the play in the wastegate valve means that the actuator arm moves around 5mm before it can take up all that slack, so they can't operate correctly. They turbos sound horrible, and eventually they will become very unreliable, Try to sell your car with this going on!!
Ive been into my local BMW dealership and its been no help, so we took the turbos off & into BMW and showed them the problem and they said no help. The turbos are £485+ VAT each from BMW and mine are manufactured by mitsubishi for BMW. You also need all the gaskets and seals fresh oil and filter at about another £100+VAT and BMW wanted 10+ Hours labour at £135+VAT per hour.
THE PERMANENT SOLUTION IF YOU HAVE THIS SAME PROBLEM IS:
This is when you have removed the turbos from the car! (I got the turbos removed by my local garage who quoted me £350 to take them out and put them back in once finished) believe me its a big job, everything is in the way!!
I have found a turbo specialist who has taken both my Turbos and has remanufactured the following parts correctly;
Titainium bush through the turbo body for the wategate arm
Remanufacturer the actuator rod to wastegate arm bush, of a greater quality.
Remanufacturer the Wastegate valve, of greater quality.
The guys are called 'Turbo Developments & Engineering'
Telephone Adam 0208 560 3927.
I am nothing to do with this company and completely un biased. They are just doing this job for me right now.
I hope this helps, I will upload the 'before' video clip asap and when I get them back from repair the 'after' video.