help diagnose misfire🙏
i have a 2003 audi a4 1.8t 290,000 km manual , main changes it’s got a stage 2+ tune catless downpipe magnaflow exause, audi TT fuel injectors and coil packs from a 2.0. i’ve had this car since march and got it from a work friend, while owning it a few weeks in a subtle kind of hiccuping feel would happen when accelerating up hills, over time it changed to hills and accelerating fast, i noticed oil in spark plug tubes and replaced plugs and valve cover gasket with an oil change, this cleared it for about another few weeks before returning in the same order, hills, accelerating and now almost all the time, i’ve noticed it consistently misfires with boost >0psi while only sometimes while under. i’ve used an obd2 to find the cylinder and switch coil packs but no change, ive also got a coil pack harness waiting to put it on. if anyone is able to give me some tests i can do or has an idea of a diagnosis please let me know.