Mid wale do means coil placed on third cylinder shares ignition lead at #2 cylinder so if that particular coil is not able to produce enough spark.
And moving on to tapets. Tell that mechanic to show u tapet readings. Since aisi baatein hawa mein nai hotin. Agar tapet ki awaz nai hai to tapet ka no scene...
And yeh liana mein common fault hota hai ek coil bad hoti hai to us se nikli lead b usi coil ka current agay derahi haina so dono mein ye scene hojata hai.
Valves ki baat karen agar toh, idle rough hoga buht and compression test would clearly tell you the difference of valves..
So stick to coil first, it might be short, broken etc.