Flashing cel for few seconds then disappears under load

Right where do I start, o yeah that's where I hate my car lol, jokes aside I've been chasing a bugger of a misfire and poor running for over a year I've tried coil packs, crank sensor, can shaft position sensor, new recirc bov, knock sensors, spark plugs, stripped every bit of pipeing/vacuum lines replaced with new and a front 02 sensor. so I gave up sent it to tuneing developments they diagnosed a fault with the connectors that conect the coil packs to the loom repaired them and put a cleaned up map on the car nothing for power but a nice 230bhp across the board well a week goes by and now it's acting up seems to pull power in the higher rev range (4500-6000) and the cel  will flash and after a few seconds disappears doesn't do it every time but quite regularly 1 in 5 pulls id say also rev hangs a bit changing gears (think it might be a sticky throttle cable)  any help would be appreciated or someone to perform an exorcism i think the cars cursed