Hello All
My father in law's 113k mile 2006 DTS with a 4.6l Northstar V8 just had its B1+B2 O2 sensors, melted cat converter, and downstream O2 sensor replaced today. I test drove after he brought it home and found the following live data while driving on a flat road at 55mph:
B1 LTFT ~ 4%
B2 LTFT ~ 6.5%
Converter temp 1200°F-1300°F

When stopped or coasting, B2 LTFT climbed to 14%

I think I have a leak I need to chase down somewhere, but my question is, is 1200°F-1300°F a safe operating range for this cat converter? With a 4.6l V8 all funneling through 1 converter it would make sense to me, but I need confirmation from someone who knows what they're talking about.

Thanks,
-Mark