Dave,
* How long does the lean AFR last?
- Until the 3-2 downshift occurs.
* Does it persist for more than 1 second while accelerating?
- It stays lean during accel.
* How are you controlling the vacuum level the engine encounters?
- I have a guage inside that I use to observe the vacuum. I am not sure that I answered your question though.
* Are you loading the engine with the brakes or up a long hill?
- No. Just a slow steady increase of speed from a stop but not enough for the 3-2 downshift to occur.
* Lastly, do you know if the secondaries are starting to open during your acceleration runs?
- Not for sure, but I am trying to stay out of them to tune this issue. I am going to disconnect the seconds on my test drive and test a couple of changes on the primary side.

* The AP should only cover a short duration lean period immediately following the throttle opening, unless it dumps too much fuel, which will then require the motor some time to recover from. It is possible that the total volume from the pump is correct, but the timing is not optimal. This could be particularly true on the secondary side if those throttle plates are starting to open, since you did a bunch of work to limit the accelerator pump volume coming on that side.
- Good point. Maybe while I am trying to stay out of the seconds, they are actually starting in and causing the lean period. Once I retest with my seconds disconnected, maybe I should go back to the 60% secondary delay (currently 40%) and see if this changes.

* I might be influenced by your answers above, but the other thought I have is that the lean spot is actually occurring before the PV opens. The PV might not be opening at the right point, and the wideband also has a bit of latency in it, so the AFR will be a lagging indicator.
- The lean spot is definately happening before the PV opening. I am using a 9.5 but I also have a 10.5 to test with. But with the lean spot happening upwards of 12hg, I am assuming that it is somewhere else. Now that you pointed out the secondaries opening, I might just need to delay the seconds to the 60% point or speed up the secondary cam by one hole.

EDIT: After thinking about what you wrote about the secondary throttle plates opening at my current 40% delay mode, and since I delayed the timing of the secondary cam so much to delay the volume, I bet that is creating a lean spot at 40% throttle. I am pushing down a bit on the throttle to make the 9.5pv open up. That has to be the cause!!!!!!!!!
I don't want the secondaries opening that quick, so I am going to swap the secondary linkage back to the 60% and retest.

Thank you very much for your responses. They help to pull the blinders off when I am trying to test so many different combos!!