i use a gmos lan 04 on my G5 GT . full sound system. tweets and sub .
i did stereo installs for a wile and anyone that cheaped out got just that for results.
airbag lights. and issues at the dealer with warrently since its a hack job with out the correct harness.
i look at it like this,. you pay close to $30,000 for a car whats another $120 to keep it wired correctly.
if you want to see results of even having things wired correctly as per tech sheets i have a video on utube called g5 power steering failure .. gauges going nuts things dinging and flashing and loss of power steering. a result of something wired to spec but still causeing an issue with the BCM .. it gets costly when you replace the power steering motor modual, BCM, and gauge cluster only to find out it was something else.. but hey thats life
there are people who dont mind going the cheap way. but my personal thoughts.. not for me