Hello I'm a first time Subaru owner and although I've researched a lot I can't seem to find information on a problem I'm having. To start I own a 2008 wrx hatch, the car has 145 000kms on it and I've owned it a month. The only mods to the car are a short shifter, new VF52 turbo was put in place of the TD04, and a high flow Invidia Catted downpipe, the car has been tuned to stage 2 with the Torqued for performance map. Before the downpipe was put on, the car had the P2096 code(catalytic converter below effienciency threshold) tuned to stage 1. I no longer get that code because it's blocked with the map now have an even worst issue. After stage 2 I drove the car 1000km without a CEL doing a highway trip, in the last few weeks I've been getting CEL P0301. The car idles normal, drives perfect, gas mileage is normal not running rich, I can only get the light to come on sometimes driving in 3 gear and up and only 4000rpm and up usually during hard acceleration. Sometimes I get the code and other times I don't. When I do accelerate hard, the fuel does partially cut off and I get the flashing CEL but if I don't push the rpm higher then where I feel the fuel cut out, the light turns off. I have read of other peoples situations and I don't think it's a coil pack becuz the car runs fine, nor injectors becuz the car is getting good mpg and not stuttering, as long as I don't WOT in 3+gear the CEL never comes on. I was wondering if a boost leak may be the cause, or possibly a spark plug becuz it is restricted to 1 cylinder. Could boost leak cause a misfire under high loads, or can a spark plug be the cause if the it only happens at high loads in 1 cylinder. I'm not getting other codes either. I've read through similar situations but it's been hard to find a clear answer.