Current difficulty: Runs well except will occassionaly idle high, both warm and cold.
Shutting the ignition and restarting will sometimes cure it.

History (about a year):
-Got rough run at idle with brief flash of MIL. Blink codes refer to Ox sensor, which was long past due, so I replaced it. Then she ran better than ever; no MIL; was pretty pleased with myself.

-After a couple months, new problem was rough running at speed, and increased fuel use, (dropping from 36mpg to 32). This seems to have gone away, more or less.

-Now the high idle I refered to above. After research, replaced MAF sensor, and cleaned throttle body, using the Dan Reed method. The MAF had been oil soaked by previous owner, and cleaning overcame this problem 6 years ago.

Also swapped out the O2 preheater relay. No change. Replaced a couple suspect vacuum lines too.
I could live with this, but it's become worse, and the MIL is constantly on now.
All replacement parts are Bosch.

****One other annoying thing. I can't get the MIL codes to erase. Followed the procedures listed, but can only read; not erase. Whenever this is done, the fuse for the (aftermarket) radio blows. I now pull the fuse before trying, but no luck.

Anyone care to comment? Thanks.
BTW I'm a long time reader, first time poster, so let me take this opportunity to express my appreciation.

The codes are 2341, 2342, 2111. But...these have been in there for over a year, and are what led me to replace the O2 sensor; (and swap the relay).

I can't seem to erase the DTC, per procedure in my Bentley, and it is during that operation that the fuse blows.

Don't know if I mentioned it, but when I insert jumper with ignition ON to erase DTCs, the CD player starts spinning. After about 8 secs of this, the fuse goes.

Hope that helps.

Yesterday I cleaned the Idle Air Control Valve, and the Throttle Body. (The TB has been done before.) Not very dirty, but upon restart the MIL put itself out. Ran fine too, so I thought I had accomplished something.

This morning, after about 4 miles, the foolish MIL turned itself back on. It is, however, running and idling fine, for now at least.