My first vehicle was a 1974 Honda 350-4, bought new. I noticed you changed to the 4-into-1 exhaust which was the rage then, and Honda eventually began selling them with that (~1976?). The same companies which had advertised 4-into-1 in magazines, claiming "30% more power" seamlessly switched to selling 4 individual pipes claiming "30% more power". Interestingly, the 1965 Dart HiPo came with a single exhaust because engineers found it gave more power than dual exhaust. Never liked riding a motorcycle and was thrilled after selling it and buying a used 1969 Dart slant.
