I had the same problem on my 96 w/ 3.4. The studder was caused by a bad egr valve. replaced it and everything is fine. This problem will not throw a code, so try unplugging the valve first and see if it runs better. It took me about 25-30 miles to have the cel come on but car ran great so I replaced the valve. Go online to find replacement as the stealer will rape you!
Steve