Voltage drop problem

Hi

i have a toyota landcruiser 1fz with gtx42 and a m600.

if i turn the ac and the lights on with ful beam the voltage drops. sometimes the engine dies as soon as i hit the high beam.

i replaced the alternator with one that is supposed to be with higher amp. the voltage drop decreased. now it only drops a little. i though it was okay. and it was until later when i connect the laptop to check the boost control and boost control switch. all is good with low boost 1.2 bar but with high boost around 1.7 the voltage drops and i get a warning it drops around 12.7.

also before i took off, the voltage was around 13.6 but in the end (after the trip) it was 13.0v.

i didnt know about this before because i didnt tune the car to high boost some els did. maybe he didnt go more boost because of the voltage drop? but he said he didnt go higher because the fuel pump was not good enough.

everything was good until the police took away my car for two weeks and i took it back now the voltage drops. or i didnt notice this before, but i dont think so.

what do you guy think or recommend.

maybe i need a higher amp alternator? what about racing battery 16v?

the thing that confuses me the most is that everything was okay with stock alternator and battery.

It sounds like your alternator is not up to task or you have a wiring issue and the alternator is not charging properly. You should be able to achieve a consistent 13.8-14.2 volts with the engine running, regardless of boost or rpm. The current requirements for the alternator will be totally dependent on the systems running in the car. A auto electrician will be able to bench test your alternator and confirm how it is performing.