The generator matrix

 1  0  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 0  1  1  a 3a^2+2 2a^2+3a+1 a^2+3a  0 a^2+3a+3 3a^2+2a+3 2a^2+3  2  a a+2 2a^2+3  2 2a^2+2a+3 a+2 3a^2+2 3a^2+2a+2 3a^2+2a+2
 0  0 2a^2+2 2a  2  0 2a+2 2a^2 2a^2+2a+2 2a^2+2a 2a 2a^2+2 2a^2+2a 2a^2 2a^2 2a^2+2a+2 2a^2+2a  2 2a+2 2a^2+2  0

generates a code of length 21 over GR(64,4) who´s minimum homogenous weight is 135.

Homogenous weight enumerator: w(x)=1x^0+1344x^135+161x^136+2240x^140+4480x^143+140x^144+15680x^148+8512x^151+84x^152+91x^160+35x^168

The gray image is a code over GF(8) with n=168, k=5 and d=135.
This code was found by Heurico 1.16 in 0.0592 seconds.