Answer:
No minimal pairs.
Environment [ s ] : beginning; inside.
Environment [ ʃ ] : beginning; inside.
Before [ s ] : [k], [l], [a], [I], [u].
After [ s ] : [a], [u], [I], [ə], [e].
Before [ ʃ ] : [I], [ŋ], [o], [n], [a].
After [ ʃ ] : [i].
The sounds [n], and [ ʃ ] are two allophones of same phoneme, they are in a complimentary distribution: [ʃ] appears only after [I], whereas, [s] appears everywhere else. Hence, y/sy/ must be the basic phoneme.