The generator matrix

 1  1
 0 a^7*X+1

generates a code of length 2 over F9[X]/(X^2) who´s minimum homogenous weight is 8.

Homogenous weight enumerator: w(x)=1x^0+144x^8+16x^9+5184x^16+1152x^17+64x^18

The gray image is a linear code over GF(9) with n=18, k=4 and d=8.
This code was found by Heurico 1.16 in 4.29e-005 seconds.