Do you happen to know which brand of IVIG you are receiving?

IVIGs are different in the way they are prepared and contain different additives. some contain sucrose, some glycine. some come as liquid and others are lyophilized (powder form) etc.

the side effects you are experiencing may be related to the additives and not the IVIG itself, and may improve with a different brand, that does not have the same additive.

Also, it sounds like you could benefit from a bipap. did you ever have formal respiratory tests/ sleep study?