In a normal Ford I6, with a conventional 1 bbl carb, you might get 2.5 numbers of air fuel variance toggling between cylinders from 1000 to 5000 rpm on a dyno run. if you use an isolated runner exhaust, and individual wide bands or you can actually check it easy.
As boost ratio goes above 2, Its nothing to be running 15 (stoich) at cyl 3 and 4, and 10 at any one of the other cylinders; conventional thought says Cylinder 6 is supposed to be richer, but no 1 is supposed to be leaner at 15 in unfavourable conditions.
And then there is fuel drop out which then creates a psychotic swing. Drag cars are easy; you just read plugs or cylinder pyros, and adjust out excessive rich or lean.
Ford subtly changed the log from its C1 coded 144/170 days to the highly evolved and refined D8 dog turd you are now turboing...even if you moderted boost, fuel in the cylinder might drop out and not be even.
Best ever non V8 in line ntake manifold? The EAO Pinto 2000. Books exist on that one, and the turbo guys in Eurpe find the 2 liter Pinto makes more power 2-bbl 34 DTML than port EFI. The later 2-bbl Lima 2300 close second, lot or work went into getting inform efficency in those. EFI Turbo intake is great with a four corner center squirter 660 or 700 carb, But the Ford small I6 intake can only be approximately modled in a flow net diagram, and the tendancy for air fuel mix drop out defined and variance cylinder to cylinder can be done only to a degree. Its the ultimate log jam head.
The guys at Ford just dynoed that in Australia, the result was the 2V head. In Argentina, the result was the 2-BBL Holley 221 SP and Solex 34 2-bbl 188 cube ME heads. In the USA, the V8's were the step up option, so a 2V head just wasn't in the hunt. Best result for flow efficeincy was the EO to E1 castings.
Here's proof of Dearborns smarts.
1978 2-bbl experimental head with calibrated valve springs, and sensor for dyno tuning the EGR. Look at how much bigger the log is, and how the 2150 Motor craft base lookes like it gets fuel to the cylinders quicker by having each barrel almost an inch appart.
Ther never was an M code 200 2-bbl....it was just another experiment. That year, they down graded the rod...to cast iron...
Each time Dearborn made changes, they increased carb inlet , runner size and volume, and added more integrated EGR ports that did away with the crack prone ones, took the manifold pickups to the front between 2 and 1 and got things pretty even.