93 s10 blazer, problems getting code from engine analyzer

previously took my 93 s10 blazer to local parts shop and they did free diagnostics test it was my EGR valve, yesterday check engine light came on started running really rough almost dies when stopped, took it to same parts store to get tested and it said it wasnt connected could not get any reading of any sort tried a couple different places, i was told there is a fuse for these? if so where and what would the letters be representing it on the fuse box? anything will help
thanks

The cigar lighter fuse is also the OBD I (aka ALDL) connector fuse.

You don't need to take a '93 to be read with a reader. All you need is a paper clip - connect pin a to pin b, turn the key and count the flashes of the check engine soon light.

http://www.troublecodes.net/GM/

previously took my 93 s10 blazer to local parts shop and they did free diagnostics test it was my EGR valve, yesterday check engine light came on started running really rough almost dies when stopped, took it to same parts store to get tested and it said it wasnt connected could not get any reading of any sort tried a couple different places, i was told there is a fuse for these? if so where and what would the letters be representing it on the fuse box? anything will help
thanks

What was the code no?
what was done about the EGR valve problem?
Have you checked the egr valve for stuck open or carbon ball under plunger?