The O2's are a total PITA on the Hemi, and I finally gave up and paid to have it done, which made a notable improvement with low end torque, throttle response and upped city mpg
The MAP is a bit of a PITA too, (what isn't on these ? ) as you have to break the plastic posts off the back of the intake manifold to install a new one. I just installed another new MAP and at 140k, the hemi runs way better than when it was new, no noises or ticks, perfectly smooth from cold weather startup to hot, 0-60 times currently 5.4 ish. and HWY mpg over 22, which is 5 mpg better than when it was new.