Am having a couple of issues with my05 altea sport 2.0tdi 140. The heater / ac it's the one with the knobs. Is only working in full power . Is there a known fix for this. The engine light is continually coming on its a code linking to the maf sensor but I swapped the maf with another and it's still coming up. Car is running very rough in spots it will accelerate fine but as soon as you are crusing it starts to drop power then come back and repeat. There is also a lot of smoke on hard acceleration. I had the egr replaced 6 months ago. I've checked vaccum hoses and they are all fine. Any checks I could do.