So I'm driving ollys old mk3 bready 16v conversion running EFI. The alternators died so have replaced it with another (secondhand) 55A mk3 alternator which is charging very slightly but nowhere near what it should do, about 12.6v and it won't compensate for when lights are switched on. I know this is the alternator most people use but surely mine will be drawing more power due to the injection compared to carbs, do I need a different alternator?

If so what do I need? Or will buying a brand new 55A mk3 one do the job?

a voltage regulator will most likley restore your one to full power , they're about £10

id imagine it might be enough when working , the mk2 doesnt have much else electrics to worry about

Where are you taking the voltage reading from ? Alternator or battery ?

Where are you taking the voltage reading from ? Alternator or battery ?

x2. Voltage drop over the cable?

Was taking readings from alternator and battery, also did continuity checks on wiring. Turn out I had 4 foobared alternators, shelled out £130 for a 65A new Lucy's alternator for GT and it's all good!