2001 Impala, alarm problem

I am a consumer--know nothing about installing alarms.  Had a reputable shop install an alarm in my 2001 Chevy Impala after a break-in I experienced last year.

Their "basic" alarm at the time of installation was a Baretta M-2.  From the beginning, this alarm was very sensitive.  It didn't take long before the alarm would sound off without being provoked.  I took the car back to the shop, and they turned the sensitivity down and told me that my car battery was on its way out.  They said that if I replaced my car battery, it might solve the alarm problem.

Last week, my car battery finally went dead (6 months since I had taken my car back to the alarm shop).  I had the battery replaced, but the alarm still sounds off on its own.

I arm the alarm, and 10 minutes later it will sound off.  Then I use the remote to disarm, wait a few seconds, and use the remote to arm the alarm again.  Less than 1 minute later it will sound off again--no provocation.  This routine will continue until I finally give up and just disarm the alarm, re-lock my doors, and pray to God nobody breaks into my car because I don't want to re-arm the alarm!

Is there anything special about my 2001 Chevy Impala that could affect the way alarms are installed so that they work properly?  Or is it the alarm itself?  Or is it the brand of alarm?  Please help with any advice.  Thanks.

Montrealler,

Thank you for your response.  I printed it out and took it to the shop last night.  The installer guy read it, used the "DirectFax document 1076" you referenced in your response, and put the diodes on.  Now my alarm is not going off after 10 minutes on its own, and everything is working properly.  Your advice was a big help!  Thanks again.

Andrea