That's pretty weird.

I dunno about the filter being directly on the AFM - for years, i had mine extended a bit longer than Lee has his and i never had any issues with boost.

Someone on the FB page had made a turbo to AFM pipe kit like yours Lee, can't remember who it was tho, but it may be worth finding out if they had any issues.

What have you done with the other hoses that are supposed to go into the original turbo/AFM pipe? Charcoal filter, ICV etc?