De-cat or not

[nominous]

When I decatted my passat which runs on veg it made a massive difference.
Less restriction and no 200K miler CAT stuff full of crud and unburnt fuel.
The car isn't modded, but the response and pickup is greatly enhanced.

Faster you can get the exhaust gases away from the turbo the better, generally.
The CAT is just a restriction in that.

Legalities are mentioned higher up.