My car lacks power in hot weather (over 90F). It is hard to drive during the day, but it is fine at night. The other problem is that it idles roughly when the engine has warmed up (regardless of outside temperature) and it has been sitting at a light for a few seconds. Oddly enough, tapping the accellerator while the break is on will cure the problem until the next time I stop.
So far I have replaced the oil, plugs, wires, ignition coil, upstream o2 sensor, fuel pump, fuel filter/pressure regulator, air filter, gas cap, and a cracked vacuum cap. It runs a lot better than it used to, but this is getting expensive!