I contacted Mahle company directly, and the following is what they said:

Today we only produce Nikasil liners for these engines and the liners are indeed the same.
MAHLE part number is 503 WR 19

Below is a table showing the MAHLE part numbers for piston, liner and assembly (matched piston & liner kit) for each engine type.

Vehicle_____________Piston______Liner________Assem bly
911 2.2"E" (155hp)___503 04 00___503 WR 19___503 04 90
911 2.2"S" (180hp)___503 03 00___503 WR 19___503 03 90
911 2.4"S" (190hp)___503 01 00___503 WR 19___503 01 90

Both the "E" and "S" pistons have valve cut outs as you can see from the attached pictures. However there are further differences. Both the compression height of the piston and the overall length differs between the "E" and the "S" piston, but more importantly the "S" piston is forged and the "E" piston is cast.
Additionally the gudgeon pin is shorter on the "S" piston (58mm compared to 66mm).