Did NIF oppose the establishment of a Knesset inquiry into its funding sources?

Not in principle. NIF welcomed the (later abandoned) proposal for a Knesset investigation into foreign sources of funding for Israeli NGOs, as long as all groups receiving such funding were to be investigated, including, for example, settler organisations, NGO Monitor (which campaigns against human rights groups in Israel) and Im Tirzu (a far-right organisation that has been critical of NIF).