Change efi or change intakes????

Map sensor issues?

I'm gonnaarmchair again...
I've seen single plains on early 273s and 318s. Factory installs. Albeit under 2bbls,lol. So seeing as we are not in the racers forum, I'm guessing this is a street car, and you want to occasionally rip up the track.
You have a 416. Since you say the combo is not deserving of a single plain, I would assume you have a small to medium cam. In which case your 416 is a torque monster down low. Soooooo losing a bit of off-the-line torque around town is no big thing.
You can get a singleP to fill a couple to several different rpm and power levels.So it would seem easy enough to find one to fit your application. It's not like putting an M1 on a teener;you have Four Hundred and Sixteen Cubic Inches.
I put a smallport/small plenum Wiand AxCelerator (single plain) onto a 360 with a small cam. Worked great! When the AG (dual plain) came out,I put one of those on. It was better up top. And in the mids. And lost/gained nothing down low. Later I put a lil bigger cam in it, and the AG is still great. This item easily pulls my 230* cammed 367 cuber,hard, to over 7000rpm. But I think the power peaks much earlier; maybe a few hundred below 6000.
In any case it seems to me, that between 5500 and 6500 either type can pull very hard, and it seems to me that the design/execution of a particular manufacturer plays a much bigger role than just the basic type.And it also seems to me that on a 416,either type of manifold can work well on a streeter with a mild TC.On a teener you have to be careful, but Ima thinkin' on a stroker,not so much.
I know nothing about racing, except it's expensive.
That's me arm-chairing.