That fuel system cleaner doesn't clean the back of the valves. So it won't do anything for carbon buildup. What it probably did for you was clean a sticky injector.I'm not too worried about getting that checked rn. I do know with APR that their tunes can be a bit more aggressive but I'm leaning towards heatsoak, fuel injectors and carbon build up. I placed an order for a CTS MQB DF IC to eliminate any heaksoak and since that was my next upgrade anyway. I was reading other forums that had similar issues to mine and they suggested Liquid Molly (Proline) Fuel System Cleaner and it completely got rid of the problem as well as the "normal" idle that sounds like a diesel, so I got one of those as well as their engine flush to go with the new oil. I'll update in 2 weeks after the IC get put on.