Originally Posted by Vinnie02
At what point on any modding that I do should I change these and to what size?
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The 19 lb injectors were replaced with 21 lb injectors in 03-04 cars. Ford discovered that the 19 lb injectors were above 90% of their duty cycle at wide open throttle... On a stock engine!
The 19's will support all of the bolt ons but they are going to be pretty much maxed out on their duty cycle.
On a street built NA engine (heads, cams, higher compression) I would use at least 21lb injectors and 24's would be preferable.