No way that I'm aware of to tell from external visual clues . 944 kits use stock cylinders bored and replated from 92 to 94 mm. A compression test should give you an idea . Every 944 piston I've ever heard of is higher compression than the stock one . My haynes manual states that on a stock engine the compression should be approximately 150 psi . My 944 with BCM pistons advertised as 11:1 is over 200 on both cylinders , with ported heads and FCR's on stock manifolds . Be advised that stock bore drop in JE 11:1 pistons will also show much higher compression than stock .