Tdc
 

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.