CAIRO -The Egyptian stock exchange said on Wednesday it will change the composition of the benchmark index EGX 30, in the first major decision made by its new chairman, Khaled Serry Siam. Effective from August, the index will drop eight companies, including Nasr City Housing and add another eight, including private equity firm Citadel Capital. In an emailed statement, the exchange also said it will replace 18 firms from the .EGX70 with the same number.