After tightening the dump valve adjustment, that didn't help. After turning the AFM in it's clamp so that it wasn't as easy to open the flap due to gravity, it helped a little, but not much. Got the manual out, and looked at how to adjust the idle speed, and check the working of the Idle Control system.
Went back to car, found adjustment screw, and below it a short length of vac hose between the TB and the cam cover.
It wasn't just split, it was broken in two (must have happened when I replaced the rocker cover bolts last week. Replaced that, idle improved, but not perfect.
Adjusted the speed (the cover stopper was already missing someone had played before).
Should idle at 600-800. Now idles roughly 800, 850 when stopping after a fast WOT run, and quickly drops back to 800. Occasionally will bounce down to arround 700, or 650 with the lights on, but much better than before and no hint of stalling.
I guess, there was me thinking the DV was causing it wo momentarily richen and confuse things.
When infact it was the broken hose letting extra air in, and weakening things.