The only reason to go for a remap instead a box is the fact that the map will be made exactly to your car, optimized. If it's failing, it's clearly a copy/paste, as we know every car/engine is different, reason why a map should be done for your car.
Someone using the same 1.8 TSI would be able to use map 3 +3, but mine the stability is map 3 +2 or 3 +1. Same engine, but again, every engine is different.
Using a box like the one I'm using, from DTUK, you may not get the full potential, but the many maps/options, will make one suitable to your engine, but again, a good remap would give better results.
If you're using good fuel, a panel filter allowing good airflow, I don't see why the car is not 100% smooth 24/7. Those two factors would allow the remap to work without problems.