Audi S3 Diverter Fluttering

Hi all.

My car was at a local garage for headcam service, valve stem seals, new valve guides, all gaskets, water pump timing belt service etc.

I fitted a Forge Splitter valve just after all of this has been done, before I had the OEM diverter and had no issues with it. Since I fitted the Splitter it doesn't matter if it's fully loose or fully tight, it would flutter, so I changed it back to the OEM one.... and it's still fluttering. I took off the vac line that goes on the top of the diverter and I'm getting vacuum.

One thing i've noticed is that there's an "psss" noise from the front of the engine, below the inlet mani, when idle, which indicates that there's obviously a vac leak, my boost gauge is reading 18 vac on idle. Could a vac leak be the cause the diverter don't function properly? I mean, not enough vac to lift the diaphragm and let off the boost? I did test the oem dv, which is a 710N, by taping the upper vac hole and lifting the diaphragm, and it will come down slowly, is this correct right?

I have a n249 bypass btw.

Car is a Audi S3 2003 BAM engine, no mods, just decat and cone filter.

Any help would be deeply appreciated, since I know flutter is no good to the turbo.

Hello everyone. I know this is a long post but I just wanted to post my solution. I took it to a local garage and the mechanic told me that the wastegate was too closed. He put it in place and now the car boosts even better and no more supra fluttering! Just a single woooshhh