need help with idle stumble

[SrS13]

I recently changed the head gasket on a 93 240sx.car ran fine for the first 40miles after the head gasket swap. However, recently after warming the car up and running it for about 20 minutes the car begins to stumble at idle and when accelerating under 2k. It is not an aggressive stumble but enough for concern and occurs sporadically.I have already assured that timing is correctly set and there are no ecu codes (other than 55). I have no mods.

I have cleaned the following parts thoroughly:- Throttle Body- Idle Air Control Valve- IAAC Valve- and the plugs that go to TPS, Distributor, Coolant Sensors, ETC.

I am not fiunding any fuel or vacuum leaks. I am becoming frustrated and cant solve this dilemma. Is there something I am overlooking?ANy help is greatly appreciated you guys have never failed me before and I only post as a last resort.

thanks

[Rev_D21]

Is the EGR sticking?

[SrS13]

if egr were sticking would i have a trouble code for it?

[sofla240drifter]

check ur pcv valveshould be changed every 50-60k miles,always gets overlooked