RebelExtrm02

iTrader: (3)

I need to get my car re-tuned and this time it has catalytic converters in the x-pipe. I know without cats the tuning shops can stick the sensor up the tailpipe. I can't see this being the case with cats because of the conversion that takes place inside them. Does this mean I need to have an extra bung welded into my long tubes for the wideband to be placed before the cats?

Cyrperformance

iTrader: (1)

From what I understand it will skew the readings so it is best to have the Wideband closest to the collector as possible. If you don't have the room or just want a simple way to add the wideband you can use one of these..
http://www.summitracing.com/parts/av...H4wxoCX97w_wcB

Chevy406

iTrader: (12)

Depends on just how accurate you think you need your AFR to be measured. I'm not qualified to answer how much the catalytic converter changes the amount of un-burned oxygen in the exhaust stream. But I'm willing to bet it isn't that much.
Another option is to just tune off fuel trims for cruise & idle but you will need a wide band to know what the WOT air fuel ratio is.

RebelExtrm02

iTrader: (3)

I spoke with a local reputable tuner and he assured me a tail pipe sensor would work just fine. He said high flow cats like mine don't do much at WOT because the gases are moving so quickly.

joecar

At WOT the cats saturate, so they will have little effect on downstream located wo2 sensor.

At PT this is not the case, the cats will alter the exhaust gas's residual oxygen content.