What do you mean by "off" slack in the cable with make them lower and tension will make them higher, but by adjusting it right to the plate and nothing more will put them in the perfect place. there is no guesswork.

If the idle really is a little high, don't forget to check your vacuum lines. If you're getting extra air from a vacuum leak, the IAC might be completely closed and unable to limit your idle speed. I saw this on a Saturn once, didn't throw any codes, still ran okay.

If the vacuum like fell off of the transmission shift modulator, that could also explain "off" shifts perhaps? Not sure exactly what that would do though, honestly. I'm thinking really firm shifts, but I could be off.