Anyone know a way to build a saved search for assemblies that have at least one component/member item where CustomField value is X AND at least one OTHER component/member item where the SAME CustomField value is Y?

Search for assembly items whose component's custom field is x or y. Group the search result by internal id. Add 2 summary criteria formula where both compare the sum to be greater than 1. 1 formula should equal 1 when the custom field is x and 0 otherwise. The other formula does the same thing with value y.

thanks @battk! that's a great idea!