[edevlin]

I had similar issues chaseing error codes when I went to headers and high flow cats. Ended up replacing both cats and lots of sensors. Take care if extending the wires for the cats, as they appear to be sensitive to resistance of wire and how they are connected.

My car is also chipped and I asked the folks who wrote the chip about changing the threshold level that was triggering the sensors CEL. I think he said mechanics could get in a lot of trouble attempting that, as you are messing with what constitutes legal emissions levels. I think my exhaust was fussy to dial in because the TTP headers did not come with any bungs (you can see a photo at my Boxster site link below my signature).

When adding bungs on a modified exhaust seems it seems like care must be taken on bung placement both how far along the exhaust stream and height of sensor tip in the exhaust stream. And as I said above how the wire for the rear sensor is extended. It funny, some folks seem to have no problem when they try the procedure, other unfortunate souls like me end messing around with it quite a bit, it was 6 months before I got it right. On the up side, it sure makes me appreciate that the car is now running great and no CEL's.....

Ed

:dance: