If I remember correcting the P0303 code is a combustion failure in cylinder number 3, P1131 is an oxygen sensor Mescla poor sensor 1, p0155 is oxygen sensor 2, p0171 Poor mixture bench 1, p0174 is a poor mixture 2 bench 2, for me you have to revive air leaks in the admission system or strangulation of one of its mangains the pulls and the departure low.