I keep getting a P0507 code that puts the car into "Limp Home Mode" intermittently. There are no other codes other than this one. When the code is not displayed the engine runs fine.... I can't hear any vacuum leaks, and the car does not have an IAC as it'* all computer controlled..... New Throttle Body?? Ideas.....??

I would check to make sure the throttle body / butterfly is opening properly & is not binding.
Have you ever cleaned the TB?
Vac leak..Spray some carb cleaner along bottom of Intake, does the idle rpm change at all?

Have you tried an idle relearn?

Also.....throw on a new PCV valve.....OEM...

Just got car and don't know history. Idles well and no "fast idle".or anything .... Seems to run fine until it goes into Reduced Power" mode. I was surprised it is showing fast RPM because the RPM seems to be fine.

Do a relearn.

I have done a relearn..... it'll run fine for about 10 minutes, then it shows the 507 code and goes into Reduced Power.....I pulled off the throttle body and it looked really really clean, but I cleaned it again what I could..... my scanner is showing that it has a high LTFT at Idle (+25-+30)...... that'* a sign of a vacuum leak..... But I ran a smoke test and don't see any smoke from anywhere except a small amount coming out from the breather which is normal....... I've got a vacuum leak somewhere I just have to find it....... I'm wondering if the EGR could be the problem........ hmmm

I'm still dealing with a PO507 code that comes on after about 15 minutes of idle...... I have replaced the MAF, and the Throttle Body.... still get the code after idling for a while..... I've noticed the Fuel trim is off.... the LTFT is 25 and the STFT is 16 at idle.... it comes down on revving the engine..... that usually means a vacuum leak. So I put my smoke machine on it to see if it was leaking somewhere...... nope.... no smoke coming from anywhere. This is driving me crazy.....

You need a factory capable scan tool to do the relearn although I'm not convinced it'll fix your problem. Quick and easy if you have the tool.

I have a GM Tech II Tool and I've done a relearn with no success.... I'm still getting high readings with the fuel trim.