Hi Mike.
Probably what is happening is that the coil
is getting more juice and is giving the spark
plugs more spark,thus creating a better
combustion of the fuel/air mixture.
I could be wrong,please correct if so.
Louis.
PS
id you have any problem installing this
alternator?
I would like to put a higher amp one in my
w123 turbo diesel but don't know if one is
available or which one would fit.