I have watched mostly all Nathan's and Doctor Dean videos and they have been very educational but I cannot figure this out. I have an 08 328xi with N51 engine. When I purchased the car it had misfires that would not go away due to burning oil from valve seals and noisy lifters and smoking. I solved these problems by replacing the cylinder head with a low mileage 2012 head. Car runs fine except for 2a99 code for exhaust camshaft correlation. I have tried all the things you guys mention...replaced solenoids, replaced cam sensors, checked bearing ledges(they are perfect). Then I opened it up again and replaced vanos actuators for intake and exhaust cam and retimed the engine with special tool all this to no avail. When I reset adaptations in INPA the code goes away and runs fine on idle then as soon as you accelerate the exhaust cam goes extremely retarded out of red range in INPA and code reappears. PIC ATTACHED.. Any info on what to try next would be appreciated.