The difference was almost 30 seconds up to Høsflot Klæbo in the skiathlon event, 10 kilometers classical + 10 kilometers freestyle.
Poromaa was frustrated afterwards and didn't think his skis were good enough.
I don't have the energy to stand here and talk about the skis, but I think when I look at the ones I'm skiing with that I'm pushing more than they are, but still losing. And that's on parts where I usually am strong. It's sad, says Poromaa in Viaplay.
"Tough for everyone"
Edvin Anger finished in 28th place. He was total second in the Tour de Ski before Saturday's race, but dropped to 10th place before Sunday's final.
It was tough for all Swedes today. I haven't been there in the sprint this year in the same way as in classical. It gets tough, says Anger.
Høsflot Klæbo decided in the last hill and sprinted to victory in the skiathlon event.
Federico Pellegrino, Italy, finished second, 2.4 seconds behind, and Jan Thomas Jenssen, Norway, third, 3.9 seconds behind.
Simen Hegstad Krüger, Norway, was many people's favorite before the race, but fell and broke his pole in the lead before the first lap and finished in 51st place.
Extended the lead
Høsflot Klæbo now leads the total in the Tour de Ski with 2.18 minutes ahead of his countryman Erik Valnes.
The Swedes were never in the fight for the podium places.
Anger, who was eliminated in the quarterfinals after a pole break in Friday's sprint, and Poromaa were good at the ski change after 10 kilometers and were only three-four seconds behind, but then Anger steadily lost ground in the freestyle.
Poromaa seemed to be hanging on, but when the pace increased, the distance to the lead remained the same for the Swede.
He held on to the main group, but was last in the group when it stretched out.
Friday's surprise man Marcus Grate, third in the sprint, finished in 58th place, almost nine minutes behind the Norwegian sovereign.
