OP - I'm sorry to hear the boa died. if you take the boa in for necropsy, make sure to put the body in the fridge and NOT the freezer. Freezing will degrade the tissue and it will not be useful for pathology testing. Depending on your vet and the lab they use, be prepared for the cost. Sometimes the reason is hard to pin down, even with a full necropsy and testing. It most likely was not IBD but I understand wanting to get the tests done to rule it out. The two I had done were in the $400+ range (for full IBD tissue pathology testing).
Alex at BoaRepublic is also working with those, I'm sure there are others. I, personally, wouldn't touch those with a 10 foot pole. Weren't all the offspring supposed to be surrendered back to the Brazilian government and that's why they changed the name to 'fire'? yeah. no thanks.