Hi Carl,
I had one of these a couple of years ago with similar problems. Turned out after much investigation that the bolt holding the pulley to the exhaust cam was loose. This had opened the key way in the pulley a bit and squashed the roll pin in the shaft oval. The amount of play was (from memory) only about .7mm which equated to about 1/2 a tooth at the perimeter. It made the engine run like a dog with a tendency to stall and low vacuum. I seem to remember I got cam sensor codes on this one. Might be worth checking cam pulleys as well as the crank one.
HTH Shaun