In all honest your parts list doesn't make much sense!
the engine ecu is not linked to the keys
the immobiliser unit is linked to the keys
the fobs are linked to the keyless entry ecu
the alarm will only activate if the keyless entry system is used
changing the alarm siren will not help the remote key entry system...
assuming your car is running there is absolutely no point in changing the immobiliser the locks or the engine ecu......
you need to get the remote keyless entry system working so you need to look for this part
http://i567.photobucket.com/albums/s...psgmw8gxku.jpg
& working fobs that are matched to that unit
also you need to consider the receiver sensor in the windscreen