6r GTI MY2013 engine light and petrol smell

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.

Given the history these engines have. I would be getting a compression test done and probably a leak down as well. Plenty of bottom end issues with these engines.

Swapping coilpacks between cylinders would be a quick way to prove a bad coilpack. But if the misfire is consistently in one particular cylinder, that's where the focus needs to be.

I work at UGP in Cheltenham, near DFO. We dont see many twinchargers, 'but we could scan it and have a quick look. Very busy ATM but if you call up, we could maybe have a look late in the week. No promises on a fix! Just advice.

Thanks for that, I should update my profile. I'm actually up in NSW now. But thanks for the offer. I'll pass on the suggestion to my mechanic and see what he reckons.

Just an update here, we've had another test drive with the diagnostic computer attached, and found the misfire has cleared with the new sparkplugs installed and the petrol smell has stopped. However, getting a new error with 'Magnetic clutch in mechanical charger' which is also throwing an engine light. Looks like a supercharger error, which mechanic says is actually in the waterpump assembly. Which I just had installed. Its an aftermarket version, he's going to put another one in to see if its the waterpump that's busted.