Throttle response could be the timing belt is off one tooth. As for the hard starting and low idle, that is typical after the battery has been disconnected. The Engine Computer must relearn "minimum throttle" before it will know when it has to be in control of idle speed. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals. Until you do that, you'll have to hold the gas pedal down 1/4" to get it started and keep it running.