Is there any kind of 'missing'? : Well not that prominent the only miss i feel is that in the sound from the exhaust which i try to minimize using the CO meter. Otherwise all cables and spark plugs are ok.
Engine consuming more oil? Any white smoke on cold starts? : I noticed oil consumption when about 5 months ago my head gasket burnt and my head had bit wear and tear near 4th cylinder corner. I got it repaired and installed and after that the engine oil tends to reduce but the plugs are clean. No white smoke in cold or warm or when reeving rpm up. Still no clue where the oil is going. No leakage as well or one that i may not have seem but will inspect and look at this more. But i would like to mention that the milage problem has been there for more than a year.
If the engine is providing bad mileage up to the extent you have mentioned, it should emit sufficient black smoke from the exhaust (on petrol). Did you scan the system through scanner? : Yes i got it scanned a lot of times. The last time i shared in this blog the values and you pointed correctly at the heat sensor as it was showing value quite low near 67 degree at full warmed engine run. This was causing the engine to eject black smoke on reeving up the engine and also hesitation. I got that replaced and scanned again and the black smoke and hesitation was fixed though i still have hesitation but that is due to the fact that i have the CO set at 2.5 to lower fuel input a bit without effecting performance that much but if i set the CO to idle petrol setting of 3.3 - 3.8 then the hesitation stops and performance is great but then the petrol consumption is ridiculous. About 5-6 with or without AC.
First of all get a compression test done to check if engine is in good nick? : Good idea. Can you suggest a good place in Islamabad to get compression test done.
All in all i have been really feed up with this problem but i know daewoo for about 11 years now and know alot on it and have put in all my effort to get this daewoo to give good mileage. All sensors are working. Scanner shows all values ok. Everything i can think of is checked and accounted for. The only 2 things (1 is suspect is the culprit then the other) is 1. Vacuum leak (Checked as much as i can and tried blocking air a bit to see if mileage improves but nothing. 2. Head and particularly Valve. I have researched that the valves and the valve spring play a very important role in performance and mileage and that if the springs are weak and the seals of valves and condition of valves themselves is bad then the intake valve lets in more fuel then needed and hence performance drops, hesitations and most of all MPG effected so as i have tried everything else. Might as well try replacing the head with the stock as this one is a GTI version which does put some doubts in my mind as the culprit as well but most mechanics say it doesn't effect it.
Sorry for long reply. Really need help. Don't have enough to buy a good car so need to get this car fit.
Thanks for the help adnan. Have a great day.