I am personally unfamiliar with Pulmonic Stenosis. I read more about it
here.After reading about it, I think the best thing would be to take your puppy to an animal cardiologist to get her evaluated.
One thing I have learned from experience with liver shunt is that protein in the diet is more difficult for the liver to process. Dogs with liver shunt have a liver that does not filter the blood well, leading to elevations of ammonia in the blood. This leads to all kinds of bad symptoms and can be life threatening. Feeding dogs with liver shunt a low-protein diet puts less stress on the liver. It is a natural way to help the dog's blood stay clean because it is simply making the liver's job easier.
Maybe feeding your puppy a low-protein diet will put less stress on its liver, and consequently the heart won't have to work as hard to support the liver's functions. You can get low-protein dog food recipes from your vet, from members on this website, or from other reputable websites. If you put a puppy on a low-protein diet correctly, it should not hinder the puppy's development. However, I would ask your vet if a low-protein diet is right for your puppy before trying it.
Definitely put as little stress on your puppy as possible until you get a full diagnosis and treatment plan in place. Don't let your puppy get too worn out from play, it might pass out. Keep your puppy well hydrated and in the air conditioning as much as possible.