Welcome to CF Mugs!
Well... The horrible clunking part is disturbing huh???
Your problem started with fuel delivery
, and remains to be a problem, so we can pretty much guess it's still fuel
You've got junk in your tank, and it needs to be cleaned... The low rev condition now is either a secondary filter is restricted, or you have enough crud in the tank restricting your pickup tube...
Try the old trick of running on a clean jug of fuel... If you are performing correctly, you need to clean out the tank, and either ditch your fuel or polish it...
Give us a better description of the clunking noise