ok...just so i don't have to go back and read through 3 pages of threads.....
have you checked to see the fuel is clean....?
are you still using the same tank of fuel.....or is it having the same problems with fresh fuel......?
have you checked the fuel filter to make sure its not blocked.....?
are you getting full throttle at the butterfly when the accelerator is flat to the floor.....dont laugh.....it happens more often than you think.....
have you checked to make sure that the metal fuel pipe from the injector pump isn't cracked and leaking.....common prob too....
and also make sure the air cleaner is clean as well......
these are some basic and free checks......if this is still the same problem with different fuel.....then theres always the chance you may have got some diesel bug.....
thats why the fuel filter needs to be checked.....give it a shake and pour some fuel out into a clean container...preferably white or glass....pour out some fuel from both sides of the fuel filter.....and see how that looks.....
im assuming you've already checked the water sedimenter in the bottom of the filter for water first......?

