Maybe or maybe not. It's not just flow that matters though. Wave pulses, flowed volume etc.
Don't get me wrong - I am as keen as the next petrol-head to get more for less. But I am seeing elsewhere documented proof that some aftermarket decat cans rob power far more notably on many EU5 systems, and not just a bit. We also saw this on the famous ZARD PENTA (the "bean can" collector later plagiarized by Mr Platt) for the 2.3L R3. Power lost.
Others did indeed add power, but with alot of DYNO time and trial and error.
But a lot of modern engines are designed by quarter million dollar computers with some really good detail orientated "digital" engineers - aiming to get the max output without compromising selling them (which is the aim after all) by being non-legally-compliant. Not somebody with a welding torch in a shed just saying - that looks about right, let's do that!.
No offense to the men in sheds, where there's a will - there's a way. But more unburnt fuel will mean emmisions fails.