hi silvergecko,
check out thread on "did you know..... fuel problem?" i recently posted a few days ago...
i had the same problem with my freda which gradually got worse until it wouldn' t rev at all...
what you might find is a clogged fuel strainer under the banjo connector on top of the injector pump, take off the banjo bolt to reveal a spring, under the spring down the hole is a small strainer about the size of a tyre valve dust cap, i levered it out with a screwdriver, give it a good clean and this may solve your probs, asuming you have done all other checks like blocked air intake, turbo not spinning up, due a fuel filter etc....
hope this helps, i'm now doing my bit as others have helped me
good luck dave