I have changed all the ignition and ECU to custom made system and the problem is that I cant find TDC precisely to have ignition fine-tuned and that is worth good 20HP. Have done some reading/searching here and what it seems is that MCDonalds straw is the most accurate method Can anyone guide me what method is the most accurate for finding TDC with engine in the car and without taking heads off.

 

You could use a piston stop and a degree wheel and find TDC just like you would when degreeing a cam.