The generator matrix

 1  0  0  1  1  1  1  1  1  1  1  1  1 (a+1)X  1  1  1 (a+1)X  1  X  1  1 aX  1  1  1  1  X  1  1 aX  1  1  1  X  0  0  1  1  1 aX (a+1)X  1 (a+1)X  1  1  0  1  1  1  1
 0  1  0  1  a a+1 (a+1)X (a+1)X a+1  1 (a+1)X+a+1 (a+1)X+1  a  1 (a+1)X+1 (a+1)X+a aX+a+1  1 aX+a  1  0  a  1 a+1  1 aX (a+1)X+1  0 aX+a a+1  1 aX+a+1 (a+1)X X+a+1  1  1  1  0  0 aX+a+1  1  1 aX+1  X  a (a+1)X+a  1 X+a+1 aX+a+1  X  0
 0  0  1 a+1  a  1 a+1  1 X+a+1  1  0  0  X X+a+1  a X+1 (a+1)X+a  1 aX+a+1 aX+a aX+a (a+1)X X+1 X+1 aX+1 aX+a+1 a+1  1 (a+1)X+1 a+1 aX X+a X+1  0 X+a aX+a+1 (a+1)X+a  X (a+1)X+1 (a+1)X+a X+a+1 a+1 aX+1  1 X+1  X  0 (a+1)X+a+1  1 X+a  0
 0  0  0  X  0  X  0  0 (a+1)X (a+1)X aX aX (a+1)X (a+1)X  0 (a+1)X  X  0 aX aX aX  0  X  X aX  X aX (a+1)X  X aX  0  X aX (a+1)X  X (a+1)X (a+1)X (a+1)X  0  0  0 aX  X aX  0 aX aX  X (a+1)X (a+1)X  0
 0  0  0  0  X (a+1)X aX (a+1)X (a+1)X aX  X  0  0  0 (a+1)X  X  X (a+1)X (a+1)X aX (a+1)X aX (a+1)X  0  X  X (a+1)X  0  0  0 (a+1)X aX  0  X aX aX  X (a+1)X  X  0 aX  X (a+1)X (a+1)X  0  X  X (a+1)X  0 (a+1)X aX

generates a code of length 51 over F4[X,sigma]/(X^2) who´s minimum homogenous weight is 136.

Homogenous weight enumerator: w(x)=1x^0+132x^136+108x^137+84x^138+468x^139+1248x^140+792x^141+108x^142+1728x^143+2316x^144+1680x^145+480x^146+3480x^147+4203x^148+2976x^149+708x^150+4308x^151+5865x^152+3660x^153+660x^154+5652x^155+6150x^156+3576x^157+564x^158+4344x^159+4104x^160+2136x^161+408x^162+1344x^163+1344x^164+432x^165+60x^166+180x^167+144x^168+39x^172+21x^176+15x^180+9x^184+9x^188

The gray image is a linear code over GF(4) with n=204, k=8 and d=136.
This code was found by Heurico 1.16 in 14 seconds.