Best mods for my 2012 VW Jetta TDI

I'm looking to upgrade my 2012 VW Jetta TDI and I'm curious about some of the best mods out there. Specifically, I'm interested in hearing about intake and exhaust upgrades, as well as any engine tuning recommendations that can give me a boost in power without compromising reliability or fuel efficiency. Any experiences and suggestions would be greatly appreciated!