engine missing when hot?

I have a 98 SW2 and it is missing or chugging when hot, generally when under load at low rpm's. I have cleaned the throttle body and the egr valve, and replaced the plugs, wires, and air filter. The car has 200000 k (120000 miles) on it and has been great so far. I was going to change the fuel filter to rule it out but when I went to pick one up from my local auto parts store they didn't stock it. I had to go to saturn and they wanted 160 bucks for one. Needless to say I didn't get it because I am really not sure if it's the problem. Then check engine light has not gone off yet and I am wondering if I can pull any codes off the car when the light hasn't gone on. Any ideas on what could be going on and if I can pull codes off the car?
Thanks,

call off the troops. turns out that the champion plug wires I put on 3000 miles ago were faulty. when I grabbed on to one today it zapped me good so I went a got a replacement set (NAPA not champion) and all's well. Thanks again.