There are differences between the Skunk2 IM and the ITR... One I can remember is that the Skunk2's diameter is 1mm less than that of the ITR IM when it meets the head...

The entire Skunk2 IM has a volume of 2.2L (at least for the B18B1), I measured it with rice (how ironic, huh)?

And this is what Skunk2 says it will do...