Before you waste anymore fuel, CAREFULLY drain out the fuel in the tank through the small bottom plug. Next, remove the the large bottom plug. Above it you'll find a sock-like affair that is meant to be a strainer for the fuel pickup tube. It will be totally crudded up and useless. Most likely, you will not be able to get it off to clean it without destroying it. Not to worry, just rip it out. Fish out as much debris as you can, screw the plug back in, and install an external filter between the tank and the fuel pump. This is a much better set up because there'll be lots of crap coming out of the tank and you'll be able to watch the filter getting clogged up, and then you replace it - repeat as necessary.

I doubt that soaking in petrol will unstick your injectors. You may want to try soaking them in carburettor/fuel injector cleaner, or even lacquer thinner or acetone. Take the rubber rings off first though, just to be on the safe side.
Good luck
Bob S.