You need to go to Lucile Packard Childrens Hospital in Palo Alto, California. There is a pediatric heart surgeron there named Dr. Frank Hanley and he is known for doing surgeries on children with pulmonary stenosis. Trust me, I know my daughter has it and she has had 3 heart surgeries so far.
Sorry, that cardiologist is JOSEPH PERLOFF. GOOGLE HIM - THERE ARE DIRECT LINKS TO HIM - HE IS THE GUY ON CONGENITAL HEART DEFECTS. HE LITERALLY "WROTE THE BOOK" GOOD LUCK!!
Dr David Perloff is at UCLA Medical Center in LA. There is a phone number you can call on their website. Ask your cardiologist if they know of him. If not, you are in the wrong place.
You want to try and see anyone associated with a congenital heart expert by the name of Perloff. My sister was born with congenital heart defects that he was able to fix. Her prognosis up until that time was heart lung transplant - You need to do the research. You are your childs best advocate.
The best advice I can give you is to take your son to a center with a large experience in severe congenital heart disease and get their opinion.