Apexi NEO, lean spike at 50% throttle?

[Ser200sx567]

I have a 97' 200sx SE-R, with an Apex'I neo and an AEM Wideband O2 sensor installed. Lately the temp's around here have droped about 30 degrees in the last week. When i'm idleing or at 100% throttle the A/F are right where I want them. But when I snap the throttle to 50% my A/F goes from 13:1 to 16:1. It also happens when I roll on and hold the throttle to 50% From 2500-5000 Rpm a gear down (the car is under high load and the throttle is at 50%) I'm going down the high way in 4th at 50%.

I can't seem to tune this out, I've tried the throttle points option and added fuel on my low throttle but it dosen't seem to fix it. I'm running the factory o2 sensor in the cat but dissconnected the one in the collector in my header and used that bung for the AEM.

Any suggestions, i'm gonna hook up my first O2 sensor and dissconnect my wide band and see if my powerband smooth's out.

[RED_DET]

What are your Lo & Hi throttle points set at? You are going lean in tip in because the hi and low % for air/fuel adjust maybe to far apart. Have you tried adjusting the high throttle settings as well? What injectors are you using, what ECU? Is the car NA or turbo? Maybe your wideband o2 sensor is going out.

[Ser200sx567]

my high low throttle settings are 40/45 now. I retarded my ignition timing and it seemed to help. The lean spike seems to happen when every i push and keep the pedal at what ever I have my high throttle settings at. It dosen't happen below my low throttle or at full throttle. It's localized at the transition stage and gets worse with a wider high/low throttle setting.

It's stays lean usually when i'm 45% throttle going up a hill (When my engine is high load).

I'm running N/A with stock injectors and ecu. I recently changed my fuel filter from stock to a Z32 one.

[RED_DET]

Try using 25/50.

[Ser200sx567]

Thanks for the info, The car is running a lot stronger and smoother. Between the fuel adjustments and Retarding the ignition timing a few degrees the lean spike is pretty much gone