Is this the grey smoke/ no power one? Sounds like timing is WAY off. Is it missing / popping? If you are certain the pump is installed correctly, then it has to be the pump. There is no real difference between the 6.9 and 7.3 pumps (there is, but internally, and they are calibrated practically the same).

 

The absolute most important thing with these engines is timing. Pumps are extremely similar(the only real difference is maximum fueling rate[with pedal floored], and that's adjustable).

Each pump is different with regards to timing -- both because of differences in manufacturing and wear over time.

You are /supposed/ to static time it -- put the new pump in, lining the marks up. Fire the truck up(the timing will be close enough to run) and then adjust with a dynamic timing tool.

However, dynamic timing tools are hard to come by and expensive. In lieu of that, you do it by ear.
Fire it up, and listen for a clatter. If it sounds like a gasser(no real clatter at idle, potentially missing higher in the revs, gray smoke), you advance the timing a bit. If it is extremely loud and smokes black when accelerating, retard it a little and see if it helps.

To advance/retard, you are loosening the three bolts holding the IP in and physically rotating it -- if the top goes towards the passenger's side, you are advancing it. Towards the driver's side retards it.

Just play with it. You can't really hurt things by messing with the timing; worst case, you set it back to marks-lined-up and try again. When timed right, it should have a little clatter at idle, and feel powerful with no smoke(except at WOT or when first firing the engine up), no missing at all.

 

At idle it runs just fine sounds good and every thing. When throttlin up it starts to sound like it has a lope and misfiring and the smore is more white I believe

 

It's retarded by a few degrees, potentially one tooth retarded on the gear.
When I first got my engine together, I was off a tooth and it did something like that - Finally got it started and it would run, but rev it up and it starts missing, lots of acrid white smoke etc.
Moved it 1 tooth further advanced, put it back together and it ran a lot better. Needed some adjustment still, but was within the adjustable range.

 

So I was having some fuel problems from the pi pump didn't even expect it had a mechanic come look at it and tell me so he told me I would have to look for a pump when I just bought a donor 1990 7.3 IDI non-turbo so what did I do I thought about it and the next thing you know it I said to myself or why not just put the pump from the 7.3 on the 6.9 so sure enough me and my husband did the swap luckily for my husband he's good with his hands we got it all off put on there and figure it out and to be really honest with you hundred percent results very nice swap truck runs wonderful now a whole new machine so if you're wondering if it works yes. It actually just bolted on like you wouldn't believe almost like it was meant to be.