6r GTI MY2013 engine light and petrol smell

[morgan s]

Hi all - hoping you can help diagnose what VW cannot. I had the engine light come on in my GTI (147,000kms), combined with coolant leak that I took in for repairs. Had the water pump replaced and new drive belts for pump and supercharger which fixed coolant leak and had a 150k service. VW could not identify source of engine light after diagnosis for a week. I've had the plugs replaced (bosch), but not coil packs yet. VW are suggesting coil pack change, but aren't sure if it'll fix it. Independent mechanic says a minor misfire is still showing in one of the cylinders that could be causing the engine light. But he's given me a list of things it could be. Rings, coil pack, supercharger, O2 sensors. I don't want to have to replace all of them if the issue can be nailed down. After mechanic clears the engine light error, it'll drive ok for a day or two before the engine light will come on at a completely random moment. I've seen it show up at low revs, on ignition, and on hill incline.

At present the running issues that might or might not be related are a lag in the supercharger, intermittent misfire in cylinder 4, and when idling after a few minutes I'm getting a smell of petrol near the drivers side window, but not at the exhaust as far as I can tell.

Any suggestions would be greatly appreciated.
thanks - Morgan.