if anyone can help....please....

I have a 93 rx7 that is having bad idle problems, i have checked the boost controller and the hose that gose to the UMI is conected and not loose at all. It turns on fine and i can drive it for a while but i noticed when it gets to a ceartain temp it starts idleing worse gradually. i notice that my boost vaccume gauge will bounce up and down between the 3 and 12 vac. along with the motor idleing bad. ive taken it to shops and asked what is wrong but they didnt know what it was exactly unless they take apart things and i dont wanna spend the money for nothing unless i know what the problem is......my secondary turbo doesnt create any boost, could this be linked to what is happening??

if anyone can help me i would greatly appreciate it