I have a 2002 WRX 5mt Cobb stage 2 with an eBay cat back, invidia Catless down pipe, a mishimoto radiator, and just the stage 2 flash. I've been experiencing a misfire (or 2) but haven't been able to fix them due to being away at school and having no where to work on my car. So on the way home for break I began to have flashing Cel and scanned it and got misfires on cylinders 2 and 4. So I replaced the spark plugs (I don't know the last time they were changed) and the codes were still there. I pulled them out re gapped them and put them back in and now there's no fault codes in the ecu, however the flashing cel is still there. Any ideas? Is this common?