My 98 GTP that I bought has crackling in all speakers except my amp and subs.

My door speakers are unhooked except for the tweeters as I found out when my window regulator went out.

I had new pioneer 6x9s installed in January and they have the noise.

I was told by bestbuy that this could be due to a factory amp. Do I have a factory amp? My car had the 6x9 in the back and another smaller speaker probably like 3 or 4"

I had the single plug harness (I have been checking around and seems like there is another for an amp bypass?)

If there is an amp and its taken out would this most likely fix my problem? Is the amp behind the glove box?