Just got a 03 si with 94k miles. Runs perfect, but after I get into the throttle hard, it'll rev up and down for a long time, like 30+ minutes... It's only after I get on it, but it always does it. Sometimes it'll rev like 1k-2.5k, other times it'll rev from 2-4k...

Coolant is topped off, I haven't bled it yet. I work at at a full shop and I plan on flushing the coolant (well all fluids). I bought the car from a friend who i the original owner, and this car has done this since it was like 2 years old. He didn't run it hard ever so he didn't have to deal with it. Just wondering if anyone know's what it 'could' be and what to look at. I'm used to working on older honda's (had a 91 prelude si and a DA integra)

 

Could be a slight vacuum leak or could be a TPS out of adjustment.

 

Clean your IACV