OK, long update, but need help, please.
I have since replaced the oxygen sensors to rule that out. I also removed and recleaned the MAF. And, I checked for vacuum leaks using the starter fluid. Since I found none, and on a whim, I shot some starter fluid into the vacuum port in the intake hose... and nothing!! No change in RPM. So, I put my vaccum gauge into the vacuum port: ZERO. I checked the gauge to ensure it was working, etc.
How is it possible that the brakes work if the vacuum port reads zero? I tried to "feel" any vacuum by blocking this with my finger, nothing.
I did remove the oil filler cap, and could hear and feel vacuum there, so I "believe" the CCV is still working.
Do I need to change just the intake tubes? Would the intake manifold gaskets have gone bad?
Any advice, please.