Skodafan20256

Hi everyone just seeing if anyone can shed some light on my problem, my skoda superb 2016 mklll 2.0 is throwing a p0299 turbo under boost fault code, the car will drive fine until harsh acceleration or revs go above 3000rpm and the car goes into total limp mode until ignition is switched off, dpf also keeps getting blocked until the point where the car is unusable and cant accelerate and randomly stalls mid driving until dpf gets cleaned again but the P0299 code is persistent and car can not be driven harshly or above 3000rpm without going into limp mode as said previously, the dpf has been cleaned out twice but on idle while stationary soot accumulation slowly builds back up with revs like the car is burning oil or has incomplete combustion, have had a number of mechanics look at it, all sensors are fine, vacuum is fine theres no leaks, turbo actuator has been checked and is fine, there is a oil leak that is believed to be the rocker cover gasket, oil is having to be topped up around every 200 - 300 miles also have the worry it could be piston rings, only main thing that has been found is that it may be the charge manifold intercooler that is blocked from carbon deposit build up on the intake causing the cars turbo to underperform and the car is only recognising the turbo under boost fault, and meaning the dpf has not got the air blowing through for a regen also not enough air for complete combustion causing that to fail, has been presumed a taxi previously and is currently on 156,000 miles, and has obviously had a bad service schedule in previous hands, dpf pressure sensor went on 155,000 and cam belt change was done due to bad water pump at a similar time, could anyone shed some light on anything that may have been missed before taking the whole manifold off and either replacing it or giving it a clean, as it is either expensive or time consuming, only other codes car is throwing is 02 sensor, only lights on the dash are amber flashing coil light and steady amber eml light if anyone could give some advise it would be greatly appreciated