I'm running unequal length pipes with split headers (maybe 4 inches overall difference) in my Bolt without any problems. I've never heard that that the pipes HAVE to be of the same length.
Some older US V8s (Oldsmobile is one, Chevy in some instances) have used exhaust manifolds that have the headpipe connections in different locations on either side of the motor. I had a 71 Cutlass like this. But I added dual exhaust and glasspacks (what else?) and it ran great. It really woke the motor up when I got rid of the stock single exhaust. Well, is sure sounded like it, anyway.
