94 lexus sc300, alarm in conjunction with oem

Hi All,
I just picked up a Compustar P2W900FMAS for my 1994 Lexus SC300 (5speed)
I know most of the other SC300 out there with aftermarket alarms are used at the smae time with the OEM on, as it's very time consuming to remove the OEM entirely. So most installation kinda piggy back on top of it, which is fine, as the stock system is very good(as far as stock ones are concerned), just that the remotes usually go bad with time.
The stock one will trigger when the hood or trunk is opened (in addition to doors)

My question is that I would like to use the existing triggers for the hood/trunk to trigger the compustar, how can I go about doing that?
Should I tap the individual OE sensors? or have the OE alarm send a signal to trigger the compustar?

This is my first big alarm install, I've wired up audio systems before, and I do 90% of the wrenching (except when a lift is needed)
I would like to tackle this on my own, instead of having someone else do it (as I get to learn by doing as well)

thanks

FYI: I do have the factory wiring manual and the compustar diagram, but I could use some pointers

also have a question wiring question
this this example the signal from the compustar going to the door locks.
in figure 1, the wire just taps the necessary door lock wire (ground)
But wouldn't the signal cause a problem since it will travel in both directions once tapped into the lock wire?

in figure 2 I have a diode on the original wire, preventing the signal form traveling back into the harness the other way

Which is correct?


thanks

Either. It's a type be locking system. A diode is not needed.

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