2019 summer race.... Jadaharabi vs 318willrun

Am I imagining things. In both videos it seems like when your car shifts about mid-track, the sound of the engine changes and it looks like the car slows down it's rate of acceleration.
Mid track that sucker should already be in 3rd pulling through. Feels smooth. Plugs look ok. Still ironing things out though.
Also first vid had speedmasters and second vid had trickflow heads. Hell I still haven't found it's happy shifting spot yet.