If you cut the hole out like that then the AFM won't work properly at all.. The reason why there's holes there of a certain size are to result in (for example) Half the air going throught the metering tunnel and half the air going through the small holes. enlarging the hole may mean more like 3/4 of the air going through the bypass and 1/4 being metered, leaning the mixtures out by 1/2, seriously lean.. The computer will put enough fuel to match the amount of air going through the metering port but there's a whole bunch more going round it.
If you haven't run it yet I would be extremely careful, you can easily melt things like pistons running lean on boost..
I remember on the 88 Mitubishi Magna AFM (similar but updated design) there were about 4 small holes, about 2-3mm some plugged, some not. I figured there were to allow for calibration in the factory. If changing 1 or 2 4mm holes could lean or richen up the mixture, imagine making a 20+mm hole..
With a chip in the computer it may work, otherwise BIG warning lights right here to prevent :o
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