Boost fading

[2000blk1.8t]

2003 1.8t stock. Normally runs good. Spikes 12-13 psi but usually ends up around 10 or 11 under power. Now, I hit the throttle and it takes off like a rocket for a quick second spiking 15 psi and fades to 5 or 6. Top end power is definitely down from usual.

[old guy]

Stock tuning shouldn't be hitting 15 psi. It sounds like your ECM is reading an overboost condition and putting you in soft limp mode.

Check the hoses from the turbo to the N75 and from the N75 to the wastegate. I suspect you are going to find a crack or split in one of those hoses. If one of those hoses are leaking the N75 can't pass the full boost pressure to the wastegate and thus the overboost condition.

[2000blk1.8t]

Thanks. I'll check it out

[2000blk1.8t]

You were right! Found a tear in the line right next to the gate. I also pulled the codes and found an over boost code.

[old guy]

Glad to hear that you got it sorted out!