| Scoot - not sure about overhauling...
...but if you're looking for replacing the calipers "cost-effectively" - I reckon you should look at the Brembo P34 clipers as fitted to the 996R, 998S and 998R.
These improve the braking fantastically - I fitted these to my SPS and they are superb!!!
They cost around £120 each new, but if you do some breaker searches you might be able to find a used pair for that price?
Other than that, its the radial Brembos or AP setups that'll cost you half a house!!!!
Good luck
Tim | 
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