Symptoms of an Intake Leak?

Still fighting cooling issues, but everytime I set the idle and drive the car more than a few miles, the idle jumps up a couple hundred rpm's.
My theory is my intake is leaking slightly and when hot the metal is expanding to seal or reduce the leak. The vacuum guage needle is shaky and bounces 1-2hg also.
Looking for some experienced opinions before I pull the intake.
Thanks.