Looking at the LIM picture the air inlet hole is huge. I wonder if your not sealing by the boost bypass hole.

Take a look at the underside of the gen 3 near the bypass valve. Is there a slot that goes around the bypass valve? I can't remember if it's on gen 3 or gen 5 or both. If it has that slot that slot must seal because that is part of the front PCV porting to the TB. That slot can not leak into the air inlet part of the LIM.

Take or find a picture of underside gen 3!