service engine soon

Try pulling the code from the ECM to see what it is indicating. Replacing the EGR valve may only have been part of the problem. O2 sensors typically last 50-60k miles so in a '95, it should be about time to replace them. Before you do this, though, get an OBD-I compatible code scanner to tell you what the problem is.

Autozone, or Advance, may be able to scan your ECM for free, and spit out a slip of paper telling you about your problem and what to do with it...... Optionally you can get a Haynes manual (recommended), it will tell you how to read the codes yourself, and it has a list of all the codes, and what they mean. BUT!..... 1995 is the only year GM produced a Hybrid OBD system in some cars: OBD- 1.5. If your diagnostic connector does not have a "B" wire (and only an "M" wire, with a purple wire 2 spaces over), then, unless Autozone, Advance, or friendly mechanic has the right scan tool, you may need to go to a dealer to get your codes scanned... but it will probably cost you. Here are a couple of Important notes:..... NOTE: Some 94 & 95 models do not have the B terminal. In which case a scanner is required...... NOTE: Some 94 & 95 models that DO have the A & B terminals still require a scanner...... All vehicles after 96 are OBDII, and require a scanner to access them...... Here's a Video you can watch which may be helpful (if you have a "B" wire on your diagnostic connector, and the OBD-I system...... http://www.youtube.com/watch?v=V8nZpQyoRh4