Hello,
Here's an update.
There is piston to car isolation, it's unlikely that the problem is with the jack.
No vibration from motor room and it's a new installation, clog doesn't seem likely.
The mufflers are not the air up kind.
Somebody from my shop who specializes in hydros came to take a look and the solution was to install a second muffler. But an MTA inspector came and shut that down, he said the long island railroad doesnt want any extra parts on a new build.
I'll keep you posted
Thanks again for the replies