Delayed/hesitant Start up

I have a 99 Disco 1(half year) and for the life of me can not pin down this rough idle at start up. This is one of 5 Disco 1's i have/had and almost all of them had this same issue at one point. The difference is when I changed the fuel pump and filter on my 96 Disco it completely fixed the problem, similar situation on the rest, always found a solution. This one I'm stumped, I've replaced the fuel pump, fuel filter(x2), the plugs, wires(even tho they looked almost new), all four O2 sensors, cleaned the MAF sensor, 8 new fuel injectors, all four coil packs, and the crankshaft sensor.... What am I missing... Any suggestions on something I over looked, sometimes a fresh perspective helps when your too close and frustrated. Thanks guys, I appreciate all the info I've got over the years, makes this hobby almost worth while(haha;D)