add on remote start to factory alarm

Ok, I'm having troubles with this install and my uncle has owned a stereo shop for 26 years and he couldn't figure it out either... so someone HELP!!! I recently installed an Ultra Start U115TL. It's designed as a remote start to add on to a factory alarm system. Everything is hooked up exactly as it says. The problem is that the trigger will not trigger. It's a positive trigger and so if I tap it on a 12V source, it will start. But when I add it into the lock system (lock system negative trigger so I use relay to change polarity), I push the lock button on the remote and it won't trigger. The relay I used closes but it still won't trigger. But if I push the lock button in the car, the car will remote start. It's like the pulse isn't large enough from the remote?? Does anyone have any ideas? Has anyone done an install like this?

Please..... year make model...

oh... I apologize... it's a 2000 Firebird. VATS system is bypassed.

You should be connecting to the (+) drivers door lock motor wire. Its a (+) output, not (-). You are connected to a wire that only gets activated when hitting the switch in the car. Assuming the Ultra has a (+) trigger input, no relay will be needed once you connect to the right wire.

Lock motor wire is gray(+) at green plug in bcm.The BCM is located in the passenger kick, just in front of the blower motor. You should also be able to get it at the drivers door harness. When you push lock on the door switch, or lock on the factory transmitter, the wire will show 12v.