We need to know what firmware you were on before you installed the custom rom. If you were on MF9 or older you can download the MF9 tar file and odin it to your phone. If you were on MJA or MK2, then you need to download the MK2 tar file and odin that.
Phones & Tablets: Galaxy S4, Galaxy Note 8", Evo 4g LTE, Evo 3D, Acer Iconia A500, Samsung Galaxy Tab 2 10.1, Ipad 2, Nabi 2,
Rom: Rooted Stock Odexed, Hotspot Mod, Xposed, Wanum