After pootling along in traffic for a few miles today, I got the chance to get past a slowcoach at the start of a dual carriageway. Didn't accelerate too hard, but the cloud of black smoke was majorly embarrassing. After getting to a clearer stretch of road I dabbed the accelerator a number of separate times, each time there was a sizeable puff of black smoke, even after giving it a good old thrash to clear out the exhaust. I have recently changed both top intercooler hoses plus the small one to the manifold. Any suggestions as to what might be the cause?

Try and get it plugged in, to see if it's throwing any codes up.

I would check the hose connections again, though if one has gone or the clip had come loose then you would get a bong. It could be over fuelling, possibly a sticky injector, or Maf issue. Have you tried cleaning the airflow sensor?

Would start there as it's easy. Possibly run some cleaner and see what happens, plugging in is a good idea too. There is nothing that can't be fixed with a hammer😜😜
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Thanks for the pointers NMJ, a good starter for 10