[calgarylumina]

I've been having a problem with my heater so I pulled out the blower motor. To do this I removed all the panels from under the dash and pulled back the carpet on the passenger side. This is my only vehicle so I had to drive it "as is" to go take care of some other business. One thing I noticed was how engine rattle I can hear with all the sound absorption under the dash on the passenger side gone. The rattle definitely got louder the more I accelerated. I'm thinking this must be the valve train. Although later I opened the hood and there is also some rattly sounds coming from the drive belt area(alternator, water pump etc..). I have a 91 3.1L. My questions are: what are possible sources of the rattle, and are the possible causes serious?