I just fixed my 2000 Alero this past weekend for under $1. It had been shifting semi-hard, jerking, service engine light, low trac light, dying when I went up hills and dying around turns for over 6 months. After checking the codes at Autozone, I thought I needed a new MAP sensor. When I went to install it, I noticed the vacuum hose that runs to the sensor was cracking and almost falling apart. So I decided to just replace this first and try it out.
Less than a dollar later my car runs perfect again!
I am not sure if this has anything to do with your issue but if my hose was going bad, then more than likely it is happening to everyone else too and would be worth looking at!
Maybe with all the mud and a potentially cracked hose, you sucked something in that you didn't mean to?