I have had the same problem! In fact about six years after GB removal I ended up with a blocked bile duct (back before they used stents w/the ECRP) and ended up w/pancreatitis! Lovely. I had horrible heartburn and tons of symptoms that replicated the pain/symptoms from the gb attacks- wierd. I still get the exact heartburn you are describing (lump in chest, radiates to back) when I am not watching my diet and not taking my Nexium regularly. This sounds odd but I have actually laid on a bag of frozen peas to ease the back pain after taking tummy meds. Probably just a mental thing as obviously not a muscle issue but I swear it works . . . . .best of luck with that. I have also had luck gulping something carbonated and getting a burp out- relieves some of that pressure. I swear it feels like I swallowed a golf ball and it is lodged in my chest sometimes- miserable.