I can't answer your question but have just installed a wideband on my 03 Dodge Ram with 5.9L and I see all kinds of readings. Most part stays right at 14.7 because of the ECM doing it's thing but I never knew air/fuel ratios swung so much.
I find this thread interesting because I have another wideband ready to be installed on my cuda. I think as long as you don't stay in the 15 or 16s at WOT for a long period of time you're OK. I believe I would try to have the spike richer than what you have at WOT but I'm not a guru when it comes to this topic.