Toyota Repair: 1993 toyota pick-up idle problem, plenum chamber, intake plenum

Question
my truck has a 22re engine in it ran great. It did not get hot but blew a head gasket and we  put a new one on. Now it will idle up and down quickly and no gas mileage.  We have had it to three shops and no one can figure out whats wrong with it.  The service engine soon light isn't on at all times and the valves have been adjusted at all three shops.  It has a new timing chain on it and a new idle air control,and a new thermostat. Each shop has had it on a scan tool and can't find anything abnormal.It has a 5-speed transmission and the warmer it gets the higher it wants to idle.
Thanks for your time and any information you could give me.  

Answer
I'm going to try to help with this but it will require some questions from me because at this time I'm a little bit lost.
In the meantime, it sounds to me like there is some sort of intake system air leak, either at the intake air hoses or between the intake plenum chamber where it connects to the intake runners or between the air cleaner and the throttle body,there is no "service engine soon light" did you mean the check engine light?
Does the check engine light ever come on?