The ALDA does not and should not have fuel in any part of it. The pressure from the intake manifold causes the ALDA to allow more fuel to be injected. In other words the ALDA limits the travel of the rack inside the IP which controls the amount of fuel delivered.
A sluggish diesel is in part a matter of opinion. Do you have an example to compare it against? This will let you know if it is really sub par. You could also try a 0-60 acceleration to give you an idea how it stacks up against others. I don't own an SD, but I think it should be in the 13s range for 0-60. What speed is it sluggish? Changed the filters lately? We need more info to be able to help.

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