Has anyone ever cam across the issue of lean AFR under load due to oil contamination whilst using the standard PCV setup on a Blobeye WRX?

I'm suffering with a rise in AFR no matter what map I run unless I specifically map for a richer situation than I think is required. My car was mapped by Mark at Thwaites and if I re load that map the issue still pops its head up. When mapped on Thwaites dyno my car ran very well but after a trip to Cornwall around 800 miles return journey a few weeks back the car will show AFR of 12.4-12.5 at full load/boost if I run WOT. I did this only a couple of times as I thought there may be an issue. I run a VF24, Pinks, V8 topmount, Toyosport 3" downpipe and 2.5" cat back from Hayward and scott. The front O2 sensor is new my wideband sensor has a new sensor fitted thinking it may be that and I fitted a walbro 255LPH pump in place of my automotive solutions 340LPH pump to eliminate that. All filters are new. The wideband isn't hooked up to my logging though so the issue is a visual one noticed under load. It will be in the future but isn't currently. I run 18.41 psi on the new map and a target AFR of 11.40 achieving 11.4-11.5 at WOT runs. The injectors are scaled to 530cc. The ignition timing is pretty conservative I think compared to how aggressive some of my previous cars have been.

So if anyone can shed any light on the issue or sound off so I can get the ideas together I'd appreciate it. I'll be making a custom Catchcan this week at work so if anyone has any designs I could look at for their subaru including internal baffles and such I would be grateful.

 

Could it be the fact you have put an almost 100lph smaller fuel pump in?

 

No. The issue is one which is present regardless of pump. The pump swap was done to eliminate a faulty pump. Pump pressure is maintained regardless and IDC never goes above 77%. The 340LPH was a little over kill for the power level I'm running but is a good pump and alternative to the Walbro but now I have both and the car has run both.