Ok, i wrote an extensive essay on the exhaust as it took me years to invest in one as i never wanted to ruin the car.
Like you i ordered the 3" turbo back system with sports cat, non resonated, non baffled system. So let me tell you here and now, this is a fantastic system, truly. At first it was tinny and decat loud on low speed manoeuvering and pull away. At first i thought it may get boomy on motorway's or whatever but it never really does.
After 600-800 miles the sound completely changed. It actually got quieter around town, but on boost the thing howls, its intoxicating and addictive. The Leon is blessed with good sound deadening so inside its loud (on boost) but not intrusive. Open ALL the windows up and boot it and the world can hear you.....pedestrians that are walking miles up ahead all look back, and my mate has commented he has heard me from a few streets away (i can second this as when my tuner drove my car after doing some logs, i could hear him absolutely 100s of yards away).
To summarise, the good:
1. Good value for money.
2. Very subtle but noisy when YOU want it to.
3. lovely burble on overun in most gears mainly 1st.
4. Gave lots more power and torque (after mapping).
5. Looks standard.
6. Welds etc are great.
7. Massive kick back of exhaust or pops when driven in anger.
The little or few problems i had.
1. The exhaust sits low to rear beam (great on standard car height, not on very low cars).
2. Doesnt come with the gaskets.
3. Exhaust goes yellow on the tip quickly, but after the first few cleans it takes a while to come back.
4. Exhaust tip rattle on the screw in the bumper above the tip. Remove before fitting.