Help- quits when put in drive

[SubBob]

'88 sub, 350, auto trans, 4WD, 1/2 ton

Truck will idle all day long in park/neutral. Will rev up good too. But when it's warmed up and put in gear it immediately begins to surge and after a little bit it will die. Don't have any trouble codes - flashes 12 only.

Replaced the following:
fuel pump & filter, MAPS, IAC, O2 sensor, distributor, plugs & wires, EGR, battery, injectors, (think that's all)

Also have set timing, checked alternator, used throttle body cleaner, knocked plug out of catalytic converter.

Nothing I have done so far has made the least bit of change. Tried driving it but won't run long enough to set codes(?).

You guys got any ideas that will fix this thing?

Will add that there is a more than slight hesitation/miss when accelerating. (This is while in park/neutral). When you first put in drive it's
'OK" for a few seconds before it starts surgeing. Acts like it's trying to find the right idle speed.

EDIT (9-7-04)
In my original post I said the engine is surging. After paying a little more attention that probably should say cutting out or missing. Seems to me it is idling way down or cutting out then picking up rpm's to normal idle. In doing so the truck will lunge a little.