I have an 02 WRX, stock intake/fuel system/turbo, catless up-pipe and downpipe (Ebay bellmouth) and 3" exhaust.
I've only had it running a couple of months. Ran fine, but when I switched it to Stage 2 91 using an old AP V1, I started getting gross misfires (flashing CEL) but only after a WOT run (or near). It would pull fine, but when I decelerated the CEL would flash for between 5-20 seconds. Cylinder one only, P0301.
I changed the spark plug and swapped the coil pack with no difference. Also cleaned the MAF and evap purge solenoid with no difference. I have a fuel filter on order.
I did a compression test on that side and it was 152 on cylinder 1 and 148 on cylinder 3. So it doesn't appear to be anything mechanical.
Any advice on where I can look would be appreciated.