i have a 97 civic hatch with h22 swap and t70 turbo. it has
been running fine until it randomly started actin up. it will rev to 2000
rpms then drop for no reason. i did put plus gas in but i dont know
if that had anything to do with it. i have replaced the fuel filter, checked
the wires, plugs, some vacuum hoses. if anyone has an idea why it
would be doin that ill try anything.

 

IACV
`

 

I would clean your Iacv. (below your throttle body)
Had the same problem in my sol, would idle at 2000 then go down to 500