i have a w plate focus 1.8lx owned for bout 3weeks or so last week it started losin power but only if tank is less than quarter full ive had it on diagnostic machine showing no problems changed leads and plugs also air filter n gunna do fuel filter also no warning lights showing can anyone help? the problems seems to occur when i put foot down and it gets to 2-3 thousand revs the speedo just drops and i have to pull over then set off again could my speedo be reading wrong or crap getting dragged through im in desperate need off advise a mechanic has said it could be one off twenty different things but i dont want to just keep changing parts and chase the problem has anyone had this happen to them ?

it does sound like fuel starvation....have you tried one of the mobile tuning guys ???worth a shot ...it could be just a blocked fuel filter.

chuck some carb cleaner through the air intake when the engine is running, you might have a blocked injector.