2004 Pontiac Montana a few issues, one at a time.idle to me seems a little low in park & drive as well as a little rough idle. really seems low on power on the hills.put the ac on the idle picks up in park & drive.the van has 180000 on it ,tryin to keep it goin right.up the hills w the ac on really kills power.changed plugs & wires & no change,cleaned throttle body no change.do not know where to go from here.any suggestions would help! thanxs