I've got a 2000 Honda Civic LX with a D16Y7(weak i know) and after the car warms up my idle drops down to something like 400rpm too about 600rpm and I don't know what causing this, the car has bout 104k miles on it. I also have another problem when I get on it and get up to about 4500+ rpm i get the high pitched squealing noise that sounds similar to a turbo spooling up but the only thing I've got one to it is just an Intake and Header. Can you guys help me out? Thanks in advance.

 

did you change or tune up anything recently?

 

nope the only things ive done to it was change out the oil and put the mods on. the idle messed up after an O2 senor went out and the squealing sound came up i think after i put this stuff called Restore into the engine which is suppose to help and reseal the cylinder walls.