i dont have any experience with this myself, but my understanding from Nascar and NHRA engine builders who have done research on the subject is that the power gains from a 4/7 swap is due to it allowing better fuel distribution on a single carb intake. if that is the case, i wouldnt think it would do much for an EFI car. also they have said along with the 4/7 swap, that swapping 2/3 at the same time results in the best gains (sometimes a .5% hp gain). on dual carb intakes where fuel distribution isnt as much of an issue, they said there were no gains. interesting that if you swap both 4/7 and 2/3, you end up with the LS1's firing order. GM engineers stated that they came up with the LS1's firing order to reduce crankshaft stress and didnt mention any power gains.