Welcome to the forum
The behaviour you are seeing is entirely normal and something they will do for life.
Rumbling and chasing is about them establishing their bond but also how they maintain it.
Right now they are in a two week period of reestablishing their bond but they are also hormonal teenagers.
There is likely also a touch of spring fever, and they will be coming up to the next hormone spike in the next couple of months.
You are likely to see a bit more dominance for the time being.
You only need to worry if they are actually fighting ( rolling around tornado which causes injuries to each other) or if bullying started to occur (which is different to normal dominance).
That means they don’t like each other and should they occur, then they would have to be separated.
how big is their cage? For boars it is essential they have plenty of room (lack of enough territory each can lead to tension which can lead to fall out) - that means a 180x60cm space. If you are using a c&c cage then that is a 5x2 grid cage.
Do all hides have two exits? Nothing enclosed with a single door should be used as that can cause issues and tensions. Both piggies need a clear way out (ie two doors) so nobody can block exits and risks fights occurring inside.
Make sure to provide multiple resources - two hay piles, two water bottles, at least two hides. You don’t want them to ever have to compete for something.
We don’t recommend the use of food bowls. Instead scatter veg and pellets around the cage and into loose piles of hay on the floor. It provides excellent mental stimulation while also meaning the dominant piggy cannot food hog.
Dominance Behaviours In Guinea Pigs
Boars: Teenage, Bullying, Fighting, Fall-outs And What Next?
A Comprehensive Guide to Guinea Pig Boars
Reacting to group or territorial changes: Dominance and group establishment/re-establishment