I am having the same problems. 2001 Focus SE Zetec and automatic
trans, only 24000 miles. The check engine light came on for the first
time ever  :x right after I bought gas on an unseasonably warm day
(maybe extra vapors in the gas tank or something) from a station I
never went to before. I read the manual it said could be bad gas so I
waited a few days like it said before doing anything. It was pinging a
little around 20mph, wouldnt accelerate unless I floored it, and after
3 days it didnt go off. I went to Autozone and got codes 401 and 402,
which mean insufficient and too much flow in the EGR valve,
(simultaneously!!! isnt that a paradox...) I went to a Ford dealer the
next morning (a Saturday) and went to see if they would fix it. I told
them I had a 400 mile round trip I needed to take this weekend, and I
wouldve left Friday night if not for the car trouble. He said it could
be DPFE which would be replaced under a Ford extended warranty for
this part (my regular warranty is long expired). He said no problem to
take the trip and come in next week. After going there and most of the
way back the light went off on its own! It was drviing noticeably
better after such a long drive. Remember my car averages only 6000
miles a year (needs to be driven more I know). I canceled the
appointment thinking I was in the clear. Last weekend it was
stuttering a little on the highway (always when passing through about
45mph) and the light came back on again. By now, 10 days and 250 miles
later the light is still on but the car is running better again on its
own and maybe the light will turn off by itself again soon. I don’t
want to go to the dealer and have them say well we repaced the DPFE
for free but you needed a new Johnson rod (that’s from Seinfeld) that
was 200 plus labor....
What should I do, just disconnect the battery and hope it drives ok
for a while or go back to Ford right away?