Throttle Body Gasket?

[shultzee13]

I have a old body style 5.7L Vortec Suburban. C1500 2WD. Idle is erratic when braking and AC is on. Have basically rebuilt truck. All new O2 sensors. New TPS. New IAC. New fuel filter. New fuel pump. Live data on code reader shows no trouble codes whatsoever. Runs great except under these conditions. I cleaned the throttle body itself about a year ago, but I did not replace the throttle body gasket. I don't hear any hissing anywhere except around the PCV valve on the valve cover grommet. I've fought this for 6 months.
I did install a new brake booster as well. No change. Both Cats replaced less than 3 months ago.
I have no codes or lights on. The EGR valve is dirty but according to scan tool is working fine. Can parts wear out and just not throw a code?

Thanks Guys
I need some help