2002 Honda Civic Alternator producing low output

If the car sits for a couple days the battery goes dead. I jump start the car and then it will run fine until the car sits for a couple days. The battery was replaced by Wal-Mart in Oct. 2009 and then again 3 wks back. The battery has a .75 amp drain on it when everything is off and the after market alarm is armed. The alternator produces 7 - 8 amps at idle with nothing on. With the headlights on high beam, brakes on, heater blower on high, and A/C on it only produces 25 - 30 amps. (I have an '01 Civic that produces ~75 amps under these same conditions.) I replaced the alternator with a new one from Honda and the conditions have not changed. Any feedback would be great.