[WardL]

Once again, great info. It is a carberated Roush 427R with 550 HP built in 2007! The bucking would occur at 2k RPM or higher. Really just any cruising speed less than 50 MPH it would just buck a little. It was smooth when accellerating, no problem. If you lugged the engine or ran the RPM up, but accellerating, no problem, it was smooth. I had a 1980 280 ZX that ran exactly the same. I think if I had a little less camshaft it would not be quite so rough. The updated carb is the best next step.