When I drive my Maxima, sometimes when I go WOT it goes real lean as indicated by the wideband, and it slows/stalls and the afr goes to like around 9, then at other times it stays at good power and descent afr. Could it be a coil pack? I replaced all plugs and the crank/cam sensors already.

 

Could be alot of things....do u have a CEL on? Any codes? Cleaned MAF, throttle body....checked injectors, FPR...many possibilities...I'd start with cleaning things first and go from there

 

Yep already cleaned the maf and grounded it directly to chassis.