Chasing lean codes (P0171 and P0174). Checked vacum at brake booster and EVAP valve. Got 18 inches at each. Is this a good number eliminating a vacuum leak?

 

Yes it is. I recently installed an electric vacuum pump to keep it higher when under load and vacuum drops off at the intake. My pump kicks off at 16inHg and doesn't run at idle because it's at exactly 18inHg at idle when I tested with a vacuum gauge. This was at the dipstick of my ADD1 catch can. It kicks on when vacuum drops to 10inhg which happens under part load.
Your issue could also be a flakey MAF sensor. If it's not reading the incoming air correctly, the ecm will either command too much fuel or not enough. In your case it could be dirty and not reading enough air thus the ecm is not adding enough fuel. Try cleaning it using MAF Sensor cleaner.
Could be dirty, clogged injectors too.
Also, the stock crankcase breather system routing it back to the intake causes a carbon buildup. As engines get older and blowby increases, this hot, oily air increases diluting the intake charge even further. Nothing good comes from this EPA mandated nonsense. It's why I route it thru a catch can or vent it to atmosphere.

 

Thanks. Cleaned the MAF with MAF cleaner. No change. Going to get some injector cleaner. Thinking not injectors because on both banks and appeared at same time.

 

I discounted injectors right after I posted for the same reason but the MAF sensor could still be not reading air flow correctly. The thing with MAF sensors is they can go flakey and not throw a code.