I'm running a stage 2 setup on my car for the last couple of months. My car is a 2018 STi and just over 25000 miles on it with a catted downpipe, exhaust, cobb sf intake, aem fuel pump, cobb fuel regulator, boost controller, ngk spark plugs and pitch stop mount. The car was stage 1 for most of it's life and never gave me an ounce of trouble. Since going stage 2 at about 23500 miles, I'm now experiencing check engine lights every 50-100 miles and my accessport is telling me it's a cylinder 4 misfire. The car begins to vibrate on startup and idle and then the dash lights up after Ive reset the ecu learning and driven for about 50 miles or so. I don't drive the car hard, launch it or anything like that. It's well maintained as is basically a commuter car. The car is currently sitting at a Subaru dealer service department. My tuner who is reputable said there isn't much he can do, but it could be a mapping issue that he needs to retweak something. But the vibration on startup is very unsettling, and my gut is telling me potential ringland failure is waiting around the corner. Another friend suggested doing a compression test. I'm not sure where to go from here. But something tells me I'll be having to order a new shortblock in the near future. I guess my question is what would you guys do in my situation? Any input on how to proceed would be appreciated.