I cant say I have lined them all up & done a direct comparison & measured the timing. They seem to have different powerbands, so it would be fair to assume the port timing is different. Maybe someone like Motorman or Topgun777 could verify either way.
it goes like this
Top quality fit and finish parts go into genuine Novarossi's
2nd level into Top
3rd level into Rex
All good parts just different levels of tolerance control. Even though those tolerance levels are extremly small (smaller than 90% of the rc racing world has the equipment to measure even if they knew what they were looking for)there is a difference in performance. Hence the reason the durability and performance of the true Novarossi is superior as is the price. you get what you pay for in many cases.