Hi After HP increase 40+ (stage 1), i have installed a diverter valve with yellow spring , i usually get vacuum leak error code (p0171 bank 1 system too lean) .. And when i accelerate i hear air sound, i wonder if the spring i use not strong enough which air escapes?
My car has 114000 miles.
My car has a manual transmission.
If by HP increase you're talking about adding multiple stage NOS kit, then your OEM OBD-II codes will be irrelevant; as the software in the ECU is not factored in for aftermarket upgrades. You'll need to contact the manufacturer of your aftermarket add on for software to download tuning information. But, yes; in most case when you have a lean situation, it's typically due to the spring being used.
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