Engine Hunting Issues

[captainlovepony]

Hi people,
        Had my 97 rx rebuilt only in december ever since had alot of hunting issues sadly the company that built engine dont want anything to do with it and will not put it right.I took it to another builder who did manage to put it right,but now after about six months is hunting again,the compression test i had 6 months ago was fine,any ideas on what maybe going on?And how it can be fixed.
 
             Thanks for your input.