Does sounds like the alternator is the problem.
If the alternator is not charging enough there will be insufficient voltage available for the ignition system and that is what stops you from going over 60km/h.

Try it during the day but with the lights on, and you could also try turning on the heater fan to see if it makes it worse.

The whistle could be your brakes locking on which would slow your speed and may be the reason your brake fluid is disappearing. But if it only happens at night then it could be your alternator whistling under load with the lights on but that wouldn't slow you down. Is it possible that one of your spark plugs has oil fouled and this is giving you slow speed and that the 'whistle' is something else?

Hello, problem again, besides the oil consumption problem..that is still unfixed...couse i can`t find segments....
The problem is: the car "wihistles"..a can`t find another word..excuse my english...someone told me that the problem would be the water pump...the strange thing is that it only whistles at night...i swear...anyway..what that big whisle can be...it is continous an annoying....
Other problem would be that i am from Romania..and i can`t find parts or any mechanic that would know anything about this car (oups..it is a datsun sunny 120Y B310) so i ask your help...
OTHER THING...when it makes the wistle i can`t run over 60KMH...with the foot on the acceleration at maximum and in the 5th gear i can`t get over 60....normally i have reached 140KMH :) and proud of it :). It consumes alot of oil...break liquid...AND AN ANOYING SOUND...on day light onl at start-up and at night all the time....
Plsssssssssssssssss tell me what can be...it is driving me crazy....can pass 60kmh and that whistle that makes anyone to look after me...