Hi Scotty. 
first of all a big thanks for helping me fix numerous problems on many cars. I am no mechanic but I’m pretty competent nowadays thanks to your Chanel.

I’ve got a f20 116i with the n13 engine with about 200k Km. I had to replace the head gasket as I over heated the engine and it was mixing water and oil in the water expansion tank. I sent the head in for a skim and the valves to be reseated. Engineers said that the head was very minimally warped so they did an extremely small skim on it and recommended that I used a standard head gasket and not over sized. I replaced the head gasket as well as all other gaskets on the engine including the main seals and the turbo feed and return pipes. I went to start the car and the car ran but kept getting a drive train error once I reverted the engine. During ideal though there was no malfunctions. After diagnostics it said that the injector cables were open circuit. I went and inspected the injector cable and found it had melted slightly due to me routing the cable to close to the engine. I replaced the injectors and the wiring harness. I also replaced coils and spark plugs. I also did a compression test and found cylinder 1 and 2 to be 9bar and 3and 4 to be 8.4bar. I also changed the vannos solenoids. 
the car will struggle to start now and will sometimes start but the revs will stay at about 500rpm and the accelerator pedal doesn’t function the error will be multiple misfires. Other times it will start up fine. I’ve checked the timing again and replaced the timing chain, guides, tensioner and vannos sprockets. Using the correct tool. I’m completely lost now as to what to do.