Civic Severely Rev Hanging/throttle sticking

So about a month ago, my 08 Honda Civic Si started rev hanging really bad. Whenever I push in the clutch to shift, it will stay at that RPM, or slightly go higher, but then after a couple seconds drop down to idle fast. The throttle will also stick for a second after I let off the pedal and then jolt. Weird thing is it doesn’t do it when I first start it or when the oil is not up to temp. Only when it’s been running for about 5 minutes. Also when i push the clutch down to let it coast, as long as the wheels are moving, the RPM will go up and down from 1,000 to 2,000 till I stop. Took it to a shop and they cleaned out the throttle body and said everything on their end looked good. They tried calling Hondas electrical staff, but apparently they were on Holiday. So annoyed when driving it, so might as well get some thoughts. The video doesn’t do all its justice, but it’s still very noticeable. Thanks!
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