check engine light.??

Hi Guys,
My Buddy`s. ride is a `92 T.C 4.6 litre v-8 . here`s the problem the check engine Light has come on and is now staying on . Appparently it would come on when he let off on the accelerator and then go out when back on the fuel after a short distance. he took it to a garage they changed some sort of sensor which is located on the EGR valve . The light was out for day or two but is now on again steady. Had it on along trip and said the car seems to run fine ,fuel mileage seemed ok ,any ideas ? He had one oxygen sensor replaced ,are there more on this model ? how about the MAF sensor any possible connection here ? What is the sensor on the EGR valve ?
Thanks:banghead:

the scensor that was replaced was probly the dpfe scensor a big problem with these cars and i believe ther is also the egr regulator but dont hold me to it im not sure what its tech name is and i would clean the maf just cuz its a good idea have ur buddy go to auto zone and get the code scanned then post it back and also what mpg was he getting? heres a link on cleaning the mafhttp://www.lincolnsonline.com/tech/00059.html

the scensor that was replaced was probly the dpfe scensor a big problem with these cars and i believe ther is also the egr regulator but dont hold me to it im not sure what its tech name is and i would clean the maf just cuz its a good idea have ur buddy go to auto zone and get the code scanned then post it back and also what mpg was he getting? heres a link on cleaning the mafhttp://www.lincolnsonline.com/tech/00059.htmlWhat`s the long version of dpfe .......?