Tien Vu

I recently bought some 420cc RX-8 injectors off Ebay(I know). At first glance, they look pretty good and seem as good as genuine injectors. I've heard offbrand injects tend to have a lot of variation, but this isn't related to the problem in having. Alright, I go to install the injectors today, everything was simple to do. I am running an AEM FIC and I go to scale the fuel map for the bigger injectors. I set the new injectors as 420 and the old as 254; simple enough. But the problem is, when I start, the car idles very badly, and my AFR reads that it's not getting enough fuel. After some messing around, i revert my fuel map back to the 254cc(stock injectors) map. I start the car and it idles almost perfectly; as good as it was before I installed the 420cc injectors. How could it be that I can idle with 420cc injectors with the stock map? Is it that my injectors are fakes/etc; but then again, there is a huge difference between 420cc and 254cc. Some help would be appreciated, thanks.