M48 alternator amperage sizing

[Beetle123]

Hello All
I have a lean miss while driving with my headlights on. I have checked my earth's and they seem fine I have a new 85 amp alternator and I'm wondering if it's big enough?? M48 seq injected with an 044 fuel pump. Car drives fine without headlights on but if you turn the lights on I get misfiring under load any help would be great

[AdamW]

There wouldn't be many cars that need more 85a so I doubt that is your issue provided the alt is working and running at the correct speed. The first step is to monitor battery voltage in motec software and compare that to what a multimeter attached direct to the battery reads. Do this with engine idling and headlights on. Hit "V" key in software to bring up view sensor screen, bat voltage should be displayed. If software reports different voltage than DVM on bat then you have a wiring issue

[Beetle123]

Thanks Adam for your reply
I have the fuel pump earthed to the fuel tank (Aluminium Drop tank) and Im thinking it could be an earth problem and Im loosing a bit of pump pressure when extra current is required when lights are turned on? i will certainly do a check that you have suggested thanks again for your help