I ran into the same issue when I retrofit a 12200411 PCM to my 455 Pontiac. The problem was that the VE table I started with was far
too low for my application. The 411 uses a VE table whose entries are proportional to engine displacement, so if your engine is much
larger in displacement than the stock calibration you started with, you will need to scale the VE table accordingly, just to get in the
ballpark.

In my case, the finished VE table for my 455 was nearly 2x that of the L31 calibration I started with in the idle/low load areas that
you'd be using when transitioning from startup fueling to the VE table. This meant that before I made the correction, as the PCM
transitioned from cranking fueling to run fueling, it would be VERY lean and would stall.

-Scott