Well you might get a tiny improvement, but I would be concerned about a change in the mixture that isnt dealt with by the standard ECU. Just how much variation can it cope with ?
On one of my motorcycles with an ECU, even changing the baffels in the exhaust required a remap to get it working properly and time on the dyno.
The power graph with just the mod to the gas flow and standard ECU was all wrong, only got an across the range improvement after re-mapping.
But its worth a try, just hope it dosent go pop