Problem Solved..!
Went to Humsafar Autos, Islamabad for quick inspection and discussed my issues. Initially they also suspected bad fuel pump coupled with bad engine wiring. They also asked to get valve clearance and injector nozzle checked as I didn't know previous maintenance history (bought car in March).
Next day Humsafar Auto team:
- found that one battery was weaker than the other and bit swollen
- replaced injector nozzles with new (old ones were worn out)
- checked valve clearance, which was within specs
- engine wiring was OK too
- they also serviced and cleaned throttle body, air intake pipes and intercooler
I also replaced both old batteries (both right (R) ones) with new ones and correct polarities. Now its starts and runs smoothly.
Mr. Saqib also said that engine is healthy and compression is good, they didn't measure it, but he further said... "we can just tell by the way it sounds and starts now"... Felt like fairies from heaven... singing in my ears
Thanks @capsat for connecting me with Humsafar Auto.
Thanks @Xulfiqar for sharing tech. insights.