the preferred way of clearing OBD-I memory codes is to disconnect the code reader while its gathering(displaying) codes. i have found that disconnecting the battery only worksfor clearing codes if you leave it disconnected for about 5 days.
first, i would replace the ECT.
2nd, clean/reclean all EGR ports and passages and verify the EGR valve is operational.
3rd, clean the MAF.
then recheck codes.