Does the car "buck" when the boost goes all over the places or is it just the guage acting up?
And by the burp, does that mean that you are getting a combustion type of noise from the car on the intake side?
The two may be related, but without more specific details, the best mechanic in the world won't be able to help you. Give details like you did with the temp. We know it happens when it is warm. But what is the cars response when this happens? Does the car loose power, buck, miss? All these symptoms are caused by different problems. Does the CE light come on, etc? If you have to go out and drive it until it gets warm just to see exactly what happens, do it. I have to at times to make sure I have the symptoms right. You can even write it down, if it helps. But you do have to be more specific.