Just replaced cat with a test pipe, and kept the stock exhaust back. Now the car act as if it is in some protect mode or something, just lost a ton of power!

Opinions on what it could be?? do i need a tune? Thanks in advance!

 

Year and model?

 

2002 a4 1.8t fwd

 

probably a boost or exhaust leak... CEL?

 

ok Thanks exhaust leak I'll tighten all the bolts to make sure the bolts to the turbo are tight but the ones to the flex down pipe aren't