need help with 02 sensor readings:civic vx

[ralphyrue]

i have searched the forum and have not found anything recent on monitoring o2 sensor readings. i have read threads:"civic vx lean burn monitor" "vx 02 sensor readings" "interpret my o2 readings" and "o2 readouts". i have a 95 cx and i replaced the engine with a 92 vx engine. the car runs good overall, i sometimes wonder if the idle is uneven at times i get a check engine light code 48 for the o2 sensor after the car has warmed up and when i am coasting to a stop while in gear. i don't get the check engine light otherwise. i have no idea how old the o2 sensor is. i pulled it and looked at it and color wise i did not see any obvious problems. i used the helms manual to troubleshoot, as has been mentioned in other posts and it all checked out until i got to the part about changing the ecu for a known good one.
i then went to the method of hooking the dmm to the d14 and d16 ecu slots, and doing the monitoring. here is what i came up with.

when engine cold i got -.78 as expected.
after engine is warm, the idle ranges between about 0.3 to 0.4
with hard acceleration about -1.5 to -1.8, normal acceleration about -0.5
while coasting to a stop goes as high as 1.8 (at this value it appears to be where the check engine light trips)
when cruising at a steady speed it seems to want to sit at 1.13

so i am getting a very wide range of 3 or greater, and the idle value seems off a bit, and when i appear to be in lean burn i am getting 1.13 instead of around 0.5.

referring to tom o's comments previously,i don't think i have an exhaust leak but could double check that. the elevation where i live is high; around 4800 feet.

recently, i got 52mpg on a 300 mile road trip, driving about 55-60mph.

is there a way to bench test the vx o2 sensor? i am unsure of what to do next. thanks for any input.