Originally Posted by TomF

Here you go:

Engine - Crankcase/Piston/Piston Ring Replacement Info.

Service
1
25/13 ENU 1010
Jun 20, 2014
The present document was valid at the time of print. A later version may be available online
Crankcase/Pistons/Piston Rings Need To Be Replaced - Mixed Installation Is Not Approved (25/13)
Model year:
as of 2008
Revision:
This bulletin replaces bulletin Group 1, # 25/13, dated June 11, 2013. Section "Information - Spare Parts Requirements" for pistons and piston rings: Text changed to "now available again".
Vehicle Type:
Cayenne S (9PA)/Cayenne Turbo (9PA)/Cayenne Turbo S (9PA)
Cayenne S (92A)/Cayenne Turbo (92A)
Panamera/Panamera S/Panamera Turbo/Panamera Turbo S
Concerns:
Cylinder liner in crankcase
Information:
If piston rings/pistons or the crankcase need to be replaced, a mixed installation can damage the cylinder liner.
NOTICE
Combination of piston rings and crankcase.
^ Risk of damage to cylinder liner.
--> Observe specifications for permissible combinations.
Due to
^ modified production methods during the manufacture of the crankcase --> from smooth honing to structural honing
^ and the use of a different coating on the piston rings (now DLC-coated)
only the combinations specified below are permitted.

--> Before carrying out any other work, check whether the cylinder liners are smooth-honed or structurally honed:
Date of Introduction:

Only engines with structurally honed cylinder liners are used in vehicles as of the shown engine numbers:
References:
--> 101055 Replacing crankcase
--> 131020 Removing and installing pistons
--> 131037 Disassembling and assembling pistons
92AAH1, 92AAI1, 92AAL1, 970110, 970111, 970120, 970121, 970410, 970411, 970420, 970421, 970430, 970431, 970440, 970441, 970450, 970451, 9PAAH1, 9PAAH7, 9PAAI1, 9PAAL1, 9PAAL7, 9PAAN1, 9PAAS1
Model year as of 2008
C02, C36