I finally got around to tuning my carbs and guess what... I actually increased my mileage from 5km/l to around 9km/l with just a simple tweak on the carburetors. (this is with twin dual side draft carbs)

Here's what I did:
- Warmed up engine for mga 15 mins (get it up to operating temp)
- turned off engine, then started from full lean air-fuel ratio, meaning the screw is screwed fully in.
- loosened idle screw to minimum idle speed (fully loosened)
- loosened the air-fuel mixture screw 3 turns out for all 4 carb throats (just 1 screw for stock carb)
- started the engine. idle should be either too high or too low, if too high then tighten the screws half a turn, if too low then loosen it. (you can do this while engine is running)
- once you get the right engine speed try to slowly tighten the mixture screw(s) without changing the engine "tone" (do this one by one for dual carbs)
- once everything is running okay you can now set the idle screw to your desired idle speed.
- for dual carbs don't expect a nice idle at once hehehe you'll need a short tube to listen to each carb throat to make sure they all "sound" the same.
- increase your tire pressure to your max "comfortable" psi. I usually have mine at 35psi front tires and 40psi rear tires (I get more oversteer this way since im driving a RWD)
- go out for a test drive and make sure your engine doesn't knock

So far this seems to work for me. I took the car out for a "touge" run and it seems to have retained the torque and HP needed to make the climb... although I had to increase my revs from 3000 to about 4000 (uphill). On normal road conditions, you'll rarely notice the difference. Except of course, the increase in mileage.

But, it MAY not work for you, but it has worked for me. hehehe