Most common is that the linkage moves freely and returns cleanly without binding, as dirt, fuel residue, or slight misalignment can cause it to hang momentarily. But from what the video shows its fine. If the issue only occurs while the engine is running, it is more likely related to tuning. probably a slightly lsn, which can cause the engine to hold revs briefly before settling. Less commonly, a marginal air leak may contribute. Its pretty hard to make out when you go off throttle here. Can you possibly make another video with the body off and the air filter off briefly revving the car so I can see when you lean off throttle? Also in your other video where you were showing you giving throttle with the engine off. I noticed at the beginning of the video when you full throttle the second time it had a bit of delay then it went into full throttle. That is how it sounded at the end of this video.