Help! No Boost - Need Your Input

[Bimmer TV]

Ok so I'm going to try and explain the situation as quickly as possible while still giving the backstory on what's been done. I currently have a boost leak again and I'm only pushing about 7psi max. Here goes.

Bought the car in April, had boost leak and rattling wastegates among other things.

After leak test and replacing boost solenoids, still no boost and leak was still present so moved on to the wastegates. Adjusted both front and back turbo wastegates and bam, now we have boost. About 17psi max - 18.2 target MHD Stage 2+. Rattle was almost completely gone for the 1st day or two but it quickly came back. Boost held though for a couple weeks.

Last Saturday I replaced the Tial Q BOV spring as I was concerned the proper one was not in there which can cause thrust damage etc. On Tial's recommendation I went with the Black 6psi spring. Left the shop and noticed that the wastegates weren't rattling or if they were, it was barely. Felt like it wasn't running right though either. Got the car warmed up and go WOT and bam, boost leak. At first I was thinking we had probably pinched the o-ring putting everything back together as it was a really tight fit and we struggled a bit (I've since remedied that issue).

We did pinch and tear the o-ring, so I sourced what seemed to be a perfect fit from the local pool supply store. (Also ordered 2 Tial ones on Amazon). Replaced the o-ring using a touch of RTV to keep it in place, still boost leak and no rattle. OK, must be the wrong spring. Checked the position of the BOV at idle, definitely way open. I had forgot the original spring at the shop and I had read the next one up (White, 8psi) was actually the proper one for these cars so I went ahead and got one on Prime.

Got the 8psi spring installed Wednesday or Thursday, BOV still pretty open at idle. After all this, seems like it was the right spring in there in the first place. At least now I know. It's the plain spring it appears, so the 10psi one.

Got back up to the shop and put the original spring back in and was excited to finally have my boost back and have a fun 1 hour ride home. Head out from the shop and still no wastegate rattle... Does seem to be responding better though but I did manage to get a CEL doing a good pull in 4th. For some reason with this particular leak/issue, I can only get the code to come up when I ask for a lot of power around 2500/3000 RPM in fourth. 30FF of course. Only about 7psi max still

At this point I thought maybe it could be the o-ring from the pool supply store but I doubted it as they felt pretty close in texture/strength and fit just right. So, I swapped out the pool filter o-ring for a Tial one and... nada. It wasn't the o-ring but at least I have 2 spares now lol.

So here I am, original spring back in which I was getting about 17psi of boost with and new o-ring installed. But now I'm only getting about 7psi and I can get it to a throw a CEL WOT in 4th. The part that really concerns me is that there is no wastegate rattle. I do hear turbo spool/whine and I am getting some boost so I'm thinking there must be an issue with the 1 turbo that was rattling. Maybe when we adjusted the wastegates, only one started rattling again after a couple days and now that one is not working or has a leak at the wastegate because it's stuck? Was it just a coincidence it happened when I switched the spring? The ride to the shop I had full boost then switch the spring (and pinch the o-ring), no boost, no rattle. My vacuum is hitting the same numbers as when I had boost and has been through this whole ordeal. Any input would be greatly appreciated. It's a real bummer going from 17 to 7psi!!!

[ShocknAwe]

Can you log the car?

Tial valve might be opening on you prematurely. Am I understanding right that you have an 8# spring in there now? Are you using the stock 1/8" vacuum line or have you tapped the manifold for a 1/4" nipple? Are you getting BOV flutter now?

I think 10-11# is where you want to be.

[Bimmer TV]

So we figured out what was going on. Somehow the wastegate arm had come disconnected from the atuator. We got it back on there last night but with no C clip handy, it ended up coming off again on the way home. At least now we know what's up and C clips will be picked up today.