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You need to collect more concrete measured emperical data:
- measure exactly how much petrol is being injected: fuel-pressure in rail, pulse-width injector is open = fuel mass being injected
- calculate optimum AFR 14.7 to 16.0:1
- sniff exhaust to verify combustion with wideband-O2 sensor, any unvapourised petrol on intake stroke is vapourised during heat of combustion. Anything not finding O2 to react with will go out exhaust
You will find:
1. carbs are sending extra unnecessary petrol into engine, extra wasted unburnt fuel will go out exhaust. Not unusual to find cruising AFR in rich 12-13:1 range and 9-10:1 under WOT
2. EFI with port-injection and O2-sensor feedback improves this tremendously. Cruising at 14.7-16:1 gives optimum combustion and mileage. WOT typically in 11-12:1 range. EFI typically gives +10-20% improvement in power and mileage over carbs
3. EFI with direct-injection improves things slightly. Primarily through use of wideband-O2 sensor feedback for tighter control of AFR under all operating conditions. WOT mixtures can now stay at 14.7:1 all way to redline. Minor +5% improvements over port-injection.
What you'll find with objective quantifiable data from sniffing exhaust is there's no extra fuel being wasted!!! High-pressure injection vapourises petrol completely! Anything not is vapourised by heat of compression stroke. AND confirmed by wideband-O2 in exhaust that there's no extra fuel being wasted!!!.
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