Yes the Bugeye has a Cat in the up pipe, will be removed when my new turbo is fitted.

Not so sure this is the problem however as it's running perfectly fine when it's only using waste gate pressure, holding a dead flat 7psi till redline etc but when the Oem controller is hooked up it's spiking and dipping all over the place.

If the cat was stuffed in the up pipe I'm sure it would be noticeable even at 7psi.

Correct me if I'm wrong..

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1989 Legacy GT --> 2001 GD WRX --> 1999 GF8 WRX --> 2001 GD WRX