I wouldnt trust a generic OBD reader both with codes and ability to clear any codes.

Before going nuts spending money, you'd need to find a proper scanner, and also learn how the ecu actually determines a misfire. Whether crank speed, via a coil, or some other method as that can give a clue as to why or whether it may be spurious.

But swapping coils etc...well...if you cant actually clear the codes to start again...If you try and clear them, how long is it before a code returns ? And under what circumstances does it happen ?