EGR Valve?

I own a 95 chevy blazer with 120k on it. While driving my car had a rough idle. I refueled and put stp in the tank. That cleared up the problem. I drove a trip around 350 miles, within 2 miles of my home the blazer began idling rough again and finally stalled. I was able to finally get it home. We replaced the fuel filter last night which was greatly clogged. The car is running better now but is still idling rough. The EGR was replaced last year. The check engine light hasn't come on. Any ideas on what this could be?

Besides the more obvious thigs like plugs, plug wires, distributor cap(if yours has one) I would look at the IAC (Idle Air Control). Causes rough idle when carboned up. Egr could be clogged up as well, depending on how many miles on it since changed.

Yip, tuneup, EGR cleaning, and CPI injector check.