I have a CEL for both banks being lean as well as idle problems and RPM surging when coming to a stop. Whenever I check my vacuum though I'm usually around 20 if not a little above. Is it possible to have that much vacuum and still have a vacuum leak I'm wondering? Or are my problems caused by something else?

 

Usually not but can be
Just as a test, with vacuum gauge hooked up unplug a smaller vacuum hose and see what happens to vacuum reading

Lean(or Rich) codes are based on computer's calculations for the OPEN TIME of each fuel injector
Say computer calculates an injector should be open for 100ms(milliseconds)
It then looks at the O2 sensor to see the Oxygen Level in the exhaust
If O2 shows high Oxygen then computer changes open time to 102ms
If O2 still shows high Oxygen then 104ms, then 106ms then 108ms, if it gets to 120ms, a 20% difference then it sets a Lean Code
Thats what STFT(short term fuel trim) is, i.e. 2%, 4%, 6%, ect.....the % difference from computers original calculation to what makes the O2 sensor see "good" Oxygen level in exhaust

In the case of Rich it would be -2%, -4%, -6% ect.....STFT

What all of this relies on are the O2 sensors, there is no backup for O2 sensors, they are "the word of God" as far as the computer goes
And................O2 sensors are THE ONLY SENSORS THAT WEAR OUT
They last 100k miles or 12 years, then they start to run out of the chemical that detects Oxygen, so..............they go LEAN, false Lean, but no way for the computer to know that
So if O2 sensors age is not known then change them first, then you can address other issues that may cause Lean codes

Since the O2s only see Oxygen exhaust manifold leaks can be an issue, they suck in air, so false lean

If you pull out a few spark plugs and look at the tips and see darker brown tips then its a False Lean, engine is actually running Richer than it should

You don't mention the year or engine size, but low fuel pressure, partially block exhaust can cause lean codes

But by far a vacuum leak or dirty MAF sensor are the common sources of legitimate Lean codes, i.e. not cause by O2s, fuel pressure or clogged exhaust

And the engine is never actually running Lean, that's not what the code means, the code means computers calculations for injector open time is off
If an engine is actually running Lean it will ping/knock all the time, if its running Rich it will blow grey smoke out the tail pipe