Tip in fueling. Ford calls them transients, or have since 1994 anyway. The car goes below .70 lambda as soon as you get back into the throttle after a shift and the fuel source is OL accel/decel enrichment...after half a second, it goes back into power enrichment and lambda resumes what is commanded in the wot driver demand fuel table. This isnt a tune issue, because the car does it with the stock tune as well...so that indicates that the transients are off and need to be adjusted. You can feel it when it happens as well, right after the shift the car is anemic and almost feels like it is about to rich-misfire. After that half second and the lambda returns to the desired wot fueling, it buzzes right along, pulling hard the rest of the way through the gear.