Respiratory training

My lungs got a bit fucked in a fire when I was a kid plus due to (genetics I think) I had about 70% lung capacity (checked a few years ago) which has increased to 80% with which I think it has topped out.

You might be the ideal candidate for one, they were designed for people recovering from lung problems/surgery/trauma and so on, also useful for people with asthma.

They basically increase the strength of the muscles around the lungs, so that you can pull more air.