As 86MLR wrote, ACE 350 is focused on most gains overall, often referenced "area under curve". Top numbers, usually near very top, often are not that different from other headers. And that is good, as when you think of it - how long do you spend near very redline? Daily driving for economy & noise reasons usually happens at low rpms. Track driving .. i better have 4/5ths the range of 4K-7.3K rpms pulling strongest/more gains/"more area under curve" then slightly higher top number (useful mostly for bragging contests) at very narrow top rpm range i see for half a second prior upshift.
I also recall reading something similar on E85 and Ace, that gains vs RON91 were smaller with Ace headers then on other headers. Imho that should be taken not as "E85 (IIRC octane number ~ 110)" is worse, rather that how good Ace works even with 91 or 93. After all - it's not that fuels of higher octane number produce more power by themselves. Higher octane number = detonation/knock has less chance to occur. Thus one can turn up boost for higher compression ratio, run leaner, adjust ignition & valve timings for more efficient instead of retarding them like on less efficient engine/intake/exhaust, that would have started to knock with fuel of worse octane number by then, and THAT ability to dial/use more efficient running mode makes/shows more power, not because "100 fuel is more powerful then 95". Think that Ace headers enhance scavenging enough to enable dialing more efficient timings even on worse fuels too rather then "having less gains" vs other headers on gas vs high octane gas, which need later to be able to use those more efficient timings/to run leaner/to use more boost. Running worse on lower octane rating fuel also shows "more gains" for switching to higher octane fuel, after all
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So there you have it - focus on overall gains instead of absolute top numbers at top rpms (where one can see biggest increases on higher octane fuels) + lot of gains from better (higher octane) fuel you simply get even on worse fuel too.