Yes, you need to set the idle up properly that's those screws on the manifold.
whats the fundamental cause though
the high current drain on the alternator, from the fan motor
How would I test that?
Its not a fault!!!! Don't start measuring amps when you don't need to!
No but by your admission you have changed fuel pressure and fixed air leaks.
Idle is fine if its setup right. And yes of course changing those things would greatly affect idle.
does the fan work okay once it kicks in? does it run fine with 12v to it? i know Ed said its probably not the cause but its also very easy to check and cross off the possibly list
too much fuel pressure so running rich on idle?