Suggestion on afr's and TP ecu code
 

MODS: ets intake, cnt rs catback, res. testpipe, cobb ap v3, boost gauge, aem wideband uego.

I've just recently put a resonated test pipe in and reconnect the rear o2 into position on the TP. The test pipe has a extended bung about 2-3 inches long. The brand is ultimate racing resonated test pipe. I'm throwing a code (p2096, Post catalyst fuel trim system. Too lean.) every now and then. I've reset it multiple time from my access port.

My aem wideband is reading from 13.8-15.3 while cruising/idle and WOT, it'll drop to 12 then goes to 11.4. I did notice a little richer (cruise and idle) after I install the resonated test pipe though.

When put in neutral from any gear, does wideband starts full rich and slowly rise to normal (14.5ish) afr's? I do know that it goes full lean with -- when let off gas but not sure of this is normal.

Why would I still get code when rear o2 is connected to test pipe? Is it mainly because of more air flow resulting this reading?

Cobb ap v3, how accurate are the knock readings? What are the most important gauge should be displayed? I know my boost gauge reads pretty accurate compare to my boost gauge. Highest knock ever read is 3 counts on stage 2 SF but mostly 1-2 on occasionally otherwise afr's seems to be right on.

Thanks.