Will turbo 4G63 Injectors fit and work in the 420A?

No.  They are peak and hold, 2-3 ohm impedance injectors. 
Ours are saturated, 12-16ohm impedance injectors.  They may
work for a little while, but you run the risk of burning up
your injector drivers, which means a dead ECU.

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If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/

Is that why 4G63's need such big injectors?

i think the stock 4G63 injectors will work OK with a turbo
car's resistor pack wired in

dsm/mitsubishi service manuals https://www.mediafire.com/folder/5k14qlaulb9s1/dsm_mitsubishi

service manuals(my whole collection) https://www.mediafire.com/folder/ac51jwwa3g1n1/automotive_manuals

Personally, i'd just pay a little more and get the right ones to begin with.

No, the turbo cars need bigger injectors because they require more fuel. Has nothing to do with the injector impedance, just the fuel requirements of a turbocharged car.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/

i'm wired and using them


Jon

1997 Eclipse RS

14.21@101mph 10/4/02