Keep 7 away from 9

Define $S$ as the set of all integers of any length such that each integer is made up of distinct digits and contains either a $7$ or $9$ in it, but not both (or else, 7 will eat 9 again, like how 7 8 9 (7 ate 9)). Furthermore, let $T_k$ represent the $k^{\text{th}}$ term in $S$ when the integers in $S$ are arranged from least to greatest (so $T_1=7$ , $T_2=9$ , $T_3=17$ , $T_4=19$ , $T_5=27$ , etc.). Find the sum of the digits of the value $T_{20014}-T_{2014}$ .