Where to begin.......It is a 98 Olds Bravada, 6 cyl (4.3 or 4.1), with approximately 120,000 miles. The transmission shifts hard (which I'm sure is partly due to needing the transfer case fluid changed- the transmission fluid is full). The main problem is that while accellerating, the vehicle will jerk and when it comes to a stop, it wants to die. Very rarely does it actually die though. This began about a week ago.
The trouble codes are:
P1133: HO2S-11 insufficient switching; ratio is below a determined number
P0122: Throttle postion sensor input is lower than expected
P1404: EGR valve stuck open
P0452: Pressure sensor
P0405: EGR sensor voltage is too low
P1870: Transmission component slipping
Okay....so far I have replaced the throttle postion sensor (which probably did not need to be changed), cleaned the EGR valve with carb cleaner (which was filthy), cleaned the tip of the MAP pressure sensor (not the fuel pressure sensor), and visually inspected the oxygen sensor-it was not grimy which I believe the ratio is too lean; nor was it white. The voltmeter read the MAP sensor at half the voltage that is specified. I read something along the lines that when something fails, the VCM will default to a different operating condition-which explains why the voltage is lower.
I'm not sure what to do next, I'm kind of overwhelmed. Thank you so much for your help!