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Hello, I have a 13 STI with a 16 STI EJ25 motor swap. I was wondering if I will need a retune for new fuel lines and a IAG FPR. I currently have the car tuned with a IAG FF kit on the car which includes the upgraded Injectors, fuel rails and fuel lines. However the IAG lines are kind of garbage and it still have the OEM FPR. As I'm taking the intake manifold off it would be a perfect time to upgrade the FPR and fuel lines. I wouldn't think these need a tune since the pressure in the fuel lines would be the same but not exactly sure how the IAG FPR would affect the system and tune. I would NOT be changing the fuel rails or injectors. Thanks for the help.
 

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I think you would not need a tune as long as your before and after fuel pressure is the same.
 

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^that

but with that said. A tuner likely wouldn’t charge you much for a tune adjustment if needed, and will likely be able to check logs to ensure it’s good if you’re worried. Both for wayyyy less than the cost of a full tune.
 

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I think you do need a tune for this changeover. The fuel pressure regulator on the EJ257 uses a manifold (i.e. boost) pressure reference to regulate the fuel pressure output (more boost = more fuel pressure to compensate for increase fuel needs). If you change the FPR and/or how the fuel pressure is regulated/controlled the fuel mapping probably needs to be changed.

Jason @Jaztuning and I worked for a long time to get my '17 to not have the fuel pressure spike resonance
at 2700 (i.e. the classic STI stumble issue). I played around with the physical plumbing for the reference with multiple
configurations and Jason had to update his mapping multiple times as we cleaned up the transition in and around 2700RPM.

What was a RPM zone that drove me nuts is now smooth as silk.

Dave
 
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