The installer of those pups may well have wired them in parralell instead of series, that will knock the output down considerably as well. Plug a lead into guitar, ensure volume and tone pots are on max, and meassure resistance between tip and shaft on end of lead not pluggged into guitar, switch between neck and bridge pups so you know what each is. This will tell you roughly what the pups outputs are, and if they come up aroudn half of what they should be, you know they have been split or wired in paralell. All without pulling the guitar apart.
If the outputs are good, have a play with pick-up heights, as others have mentioned it has a large bearing on your end result, and at times even 2 pups of the same make and model will need different height settings.
