We chased a similar problem for months, tried every thing, squirter's, timing, wedge floats, j tubes etc. We knew it was a fuel control issue as the problem never appeared on the dyno and if we induced tyre spin into the chassis it cleared. The O2 data said it was going lean then a rich spike. Turned out it was fuel just sloshing out of the vent tubes, we had to lower the fuel level in the bowls (below recommended) and all was well. This was on 2 x 1150 Dominator's BTW.