i also have keyless entry from factory but there is no alarm proctection. I installed the alpine alarm and was able to use the pop the trunk feature. I use a relay to trigger the trunk module to pop the trunk open. First, you have to locate the wire that trigger the module. It's located on the driver side kick panel. It's white wire w/ blue stripe. Then you have to splice it. That is where you add a relay. I do not have the specific detail with me but that is how it goes. ouput from alarm to relay , relay supplies with 12 volts power and grounded, ouput from relay to the trunk wire . However, for more infor. you should visit
www.the12volts.com