any ideas why all of a sudden (directly after, like within a day of my aformentioned battery issues, and a long trip, where i added a "high mileage injector cleaner" to the tank) i've got a rough idle. really it goes through the rpm range kinda rough, but will sorta smooth out at highway speeds. idle is around 800 rpm according to the tach. i've noticed a "rich" smell a little too when i get out if i'm downwind of the exhaust... by rich though, i don't necessarily mean a gas smell, like in older cars and trucks when they load up or are running rich, but more of just a.....weird, smell. also, i noticed yesterday while waiting in a drive-through, my oil pressure guage was low...until i gave it gas to move of course, then it came on up. i know this is wordy, and probably too vaigue, but the long and short of it is, my truck's running weird, and it happened basically over night. i got in it the other day, and it had a weird vibration at idle, and i'm not sure where to start....now that you've finished my first novel...any ideas?

i'll also add that i've changed the fuel filter, plugs, plug wires and distributor cap less than 10k miles ago.