Here's some more info: I have round top SU's and 280zx electronic ignition, But the engine isn't surging. I wish I could describe it better. I have had the car on level ground and let out the clutch and it's fine. I do notice it is more apt to happen at higher rpms. Could a worn front differential mount cause this? or maybe loose differential internals? When I had the rear of the car on blocks, I manually turned the rear driver-side hub forwards, and the pass side wheel turned the opposite. I know that is normal, but I also noticed there was a little play when I turned the rear driver-side hub before the pass side turned. Not much, but a little. Is that important? As far as the linkage goes, it's all brand new. The carburetors were completely gone through and new linkage installed before I bought the car. But again, the engine doesn't change rpm at all, it has to do with something from the transmission rearward... ~Richard