p0101 '03 chevy 2500hd 6.0

My truck gave off code P0101 this morning on the way to work. During lunch I cleared the code and put in a new air filter and it hasn't gone off again. I've noticed some other symptoms, such as when I brake or change PRND321 the idle drops below 500 rpm for a second and then jumps back up. It happens once in awhile. When I put it in D it sometimes can't seem to figure out which gear to be in. I've read up on code P0101 and these symptoms seem to pop up alot. I know someone will ask about fuel pressure and it is 50 psi at idle last time I checked it at the fuel rail.

I'm not a mechanic but I've got an obd scanner, fuel pressure gauge and a vac. gauge so I can run some diagnostics if some more info would help.

Tomorrow I'm going to take the air box apart and clean the throttle body just as a precaution.