[RomanCandle]

It long been known that engines in motorbikes have for years been mapped with a dip in the power curve at the rev ranges that emissions and noise tests are conducted at. Hence the popularity of Dynamometer testing and tuning even on normally aspirated bikes, and a startling improvement of responsiveness and horsepower through the rev range as a result. I wouldn't be at all surprised if this was also the norm for car engines all along prior to the more sophisticated electronic devices used today.

Back in the 90s this was always alleged to be mainly because of the extremely strict green laws in California and Europe and was a way to get around these laws without the addition of heavy power-sapping devices such at catalytic converters etc.