You will need to have it remapped for not just fuel adjustments, but ignition changes play a large role in how things turn out. The flow capacity of the inlets is increased dramatically as the choke point of the manifold is moved farther down. Where it used to be at the bell mouth (now 3mm larger at the critical dimention) and the bell mouth shape has been drastically altered from a more 'full radius' to an eliptical lead in to the runners, it will not only affect the flow characteristics but also the signal strength of the pulse wave. The VE curve will be very different and the igniton timing will need to be adjusted to suit, possibly to some very non typical values.
The main problem on the v6 inlet is the plenum volume headroom height above the trumpets, which affects distribution and total bulk flow capabilities. Same as on the nissan 350z where raising the plenum a mere 6mm can gain 10bhp.
I wouldnt be too worried right now as you have a lot of adjustments that need to be made and potential to make decent gains, you've just moved the restriction point to another point in the inlet. You have flow potential, just like a garden hose, but sticking your thumb over the end isnt going to help. Your main points now will be the plenum itself and the cylinder head, or more specifically the short side which has a horrible machining operation from the factory giving a very very nasty turn back and sharp edge right at the most important part of the port.
For an idea on how much material is removed, the ally grindings weighed in at around a third of a kilo. The bell mouth ID at the edge is over 10mm larger and the throat 3mm larger, the cylinder head/inlet manifold match has increased from 26mm to 32mm (which you can see quite well in the pictures), which is the same size as the rest of the port throat and closer a better ratio between throat/valve size. You will probably loose a small amount of torque at low rpm due to the increase in runner volume and the associated drop in velocity, but peak numbers should bump up a fair amount. But like I said, you still only have 30mm of headroom height above the trumpets, which sucks.
The runners now, without the plenum top to disrupt flow and bounce back pressure waves, flow very very close to a set of open ITB's.