This is all enlightening....but still not totally clear.

I bought this 2004 Matrix XR used. IT had a GM audio sytem with cd and cassette.

I took it out and had a car audio guy install a single width Pioneer. Reception was bad so I returned it and put in a Sony...... Still bad multipath reception.
The antenna is working because if I unscrew it from the roof I can hear distant station cut way down...

But is sounds like a poor antenna problem. I dont know if I blew it because it is a type2 databus????

I dont see anything else being effected accept that the rec eption is staticy even with strong city stations. As you drive around static comes in and out. I dont understand how you can put the original in the glove compartment and put a aftermarket radio in the slot at the same time???/ There must be another way.
ANy info would be appreciated.