Welkom Schalk !
The original wheel caps were probably more aerodynamic than the alloy wheels
Do you really need those mudflaps ?
Deleting them will improve your fuel economy.
If you often drive with the windows open, the winddeflector may actually be usefull. Try it out at your usual speeds.
More noise normally also means more wind resistance.
This hypermiling thing surely makes your car and yourself look like an old fart
Tracking your exact fuel use is quite important to see how you're doing.
So fill up completely for once, then go to the fueling station when you think around 200 Rand worth of fuel can go in.
By not filling up completely, you're always guesstimating.
Even so, less than 7 L/100km is OK for a carburetor 1.6L .
The mirrors could also be made more aerodynamic, as they are quite flat at the front.