I'm feelin' the same thing in my car.
I thought it was slack in the cable between the IMRC and the secondary linkage, but Demon nixed that idea.
My plugs and wires are brand new. Maybe 2k on them. I changed them a good month before I moved up to UT with no problems noted. On my move up to UT I noticed detonation at part throttle, then my fuel pump failed. Changed the fuel pump, haven't heard any detonation since, but now I have the fluttering at light throttle.
I guess I'll go check my plugs/wires, as it's an easy place to start. I changed my fuel filter when I changed my plugs, which was pre-pump failure. Any other suggestions?
