It's a combination of looser regs, older equipment, more ways to find loopholes (no use measuring emissions at 5500rpm if the motorbike revs to 12k when taking

It's a combination of looser regs, older equipment, more ways to find loopholes (no use measuring emissions at 5500rpm if the motorbike revs to 12k when taking off from the lights), and a culture of modifying exhaust/intake systems