I've had a misfire for quite some time now, started off by replacing the Magnecor HT leads, sorted it for a few days. Replaced the dizzy cap and rotor arm, again, sorted it for a few days and it came back. I'm going for a new set of plugs today just to rule that out (NGK Iridium heat range 7). Some people have said it could be hitting fuel cut. I know it's not the best idea but I've got a HKS FCD. It's still running ct9, roughly 0.94bar of boost. FMIC, HKS mushroom filter, relocated to the front, stainless exhaust system decat, stainless manifold, FPR, it seems too high but the fuel pressure is at 4bar, it has been since I got the car 7 months ago and it's been fine up until a few months ago when the misfire started. I've got a reconditioned 4efte with just over 70,000 miles on it. Sometimes it boosts perfectly without misfiring and other times it misses like mad! I've described it best I could and listed all the mods I can remember to help you guys figure out what's causing it. Cheers!