for the sake of try it why not just remove motor assembly suck in full air into lungs and blow into air chamber if it sounds off look for issues elsewhere if no sound then pull it apart.
you say some pins are loose as in drops in easily? if so that might be the entire issue where the plate is not sealed allowing air to go where ever it wants to. I would try disassembly of air chamber and use sealer again re-install pins and use a clamp and snug plate to air chamber and let it sit overnight. worth a try at this point nothing to lose and everything to gain I have used auto silicone gasket sealer with good results and you can still take it apart if needed.
you must be a taurus as bulls never give up!
out of curiosity can't the holes that pins go into be tapped for a screw?
