Idle Control Valve, Mas And Egr! Now What?

[Bio4x4]

I just replaced on my 1995 es300 (160k) the ICV with a new factory replacement ($200), cleaned the throttle body, MAS and the EGR valve body and checked it to hold a vacuum, new air cleaner to, all about 30 days ago. Just last night Wife and I went out after the car had been sitting for 1 1/2 hours, she started it and the rough idle and die happened. I came in the garage and she tried it again and as it started I herd a little "backfire" sound under the hood and after a throttle gun it idled. We drove it 1.5 miles and shopped for 20min started again with the rough idle but then idled fine after a moment.....Arrrrrg!!!!!

What next do I check or where do I go from here, this is a head scratcher..

Thanks in advance!