running too lean

[doomstr55]

by changing the exhaust system from one end to a another, an removing the cat will it make the car run too lean?????.....an if so will the ecu need reprograming?.....2004 specv

[boyrs]

shouldn't as long as there are no leaks in the exhaust. the MAF and first O2 sensor should control the A/F ratio. I've changed the exhaust completely and don't have a problem running lean/rich. if you delete the cat, you will need an O2 sensor spacer for the bank 2 sensor to pull it out of the exhaust stream to avoid the MIL light.