Sounds like either a misfire, or a restriction. If it is a misfire, the CEL should flash when it happens. Best bet is to read codes, but in the absence of a reader you can start with the obvious stuff ... pull the plugs and look for any discoloration, check primary and secondary resistance on the ignition coils, check resistance on plug wires, and check fuel pressure at the rail. Also, do a visual check on the entire exhaust system to see if there is any damage that would restrict flow. Change the fuel filter if it has been changed in a while.
Unfortunately, you are shooting in the dark without reading codes.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)