You either have not left enough freeplay in the cables, or one of the cables is damaged kinked or corroded somewhere up its length.
You can run with just one, but consider the second one as double-redundancy. I think the throttle is a system where it's worth having a safety margin myself, however that said the T595 I had had one cable from standard, and that never gave me any trouble at all, though they did fit a second cable on the subsequent 955i.
You can run with just one, but consider the second one as double-redundancy. I think the throttle is a system where it's worth having a safety margin myself, however that said the T595 I had had one cable from standard, and that never gave me any trouble at all, though they did fit a second cable on the subsequent 955i.