Boy good news, and the pressure build up on #4 is great as long as it's gas ,pull a tube Bull) it could be a reaction to the acid. But I think its Gas from the zone , I never found out how their set up out to Handel the gas , lots options we could sell it , reinjecked it , flare in or let it build in the casing and see what the pressure builds to. Remember the lower the casing the better it is for the fluid to move into the bore. Now if it gases off making foam you would want to keep some back pressure , to keep it fluid then you can pump it. This is where your production hand takes over and makes the well give it ,up thats operating . Think of a soda shake it up , how do you take take your finger off fast slow do you know how the soada is going to act , foam , spray , or flat , that's what wells can be .