So, recently swapped the head on my 95 B18C1 for one from a 97 and replaced the headgasket while I was in there. Did a full valve adjustment on the new head once I had it installed and everything is to spec. Now prior to swapping the head, A/F ratio at idle was around 15:1 when cold and around 16.5-17.9:1 when warmed up. After swapping the head out, I'm seeing 12-12.9:1 cold and 12.6-13.9:1 when warmed up. While driving, ratio is generally 14.3-14.9:1 cruising. WTF could be going on here? She's running like a champ, but I do have an oil leak at the head gasket on the rear, skimped on resurfacing the block but it will be done soon enough.

Additional info can be found in my build thread but here's the basic run-down of mods:
Stock P72
Skunk2 Gen1 IM
Shortram with K&N Cone
DC 4-2-1 with 2.5" Collector Mod
S2K Cat
Thermal R&D Stealth 2.5" Cat-back
GE Fuel Rail + Stock injectors + Adjustable FPR - 48PSI at idle
PLX Wideband running same O2 since I got it

 

drive the car at least 100-200 miles. it takes awhile for the fuel trims to set in the ecu. after a tank of gas is burned up you should see it fall back. the ecus are rich after a reset