OMG! Thank you so much Saarg, I've been trying the whole day to passthrough my dual interface Intel NIC. Tried with and without the "pci-stub" and "vfio-pci" in the syslinux config. Also tried to pass just one of the interfaces.... Tried so many things until i stumbled upon your post with the link for the "vfio_iommu_type1.allow_unsafe_interrupts=1" command. This should be added to the OP's post, I think.  
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