I have been having an issue with my 75 silver shadow. The carbs were recently rebuilt. I took the car on a drive of about 30 mins the other day down A1A here. its a 35 mph constant road. Did not stop the car at any traffic light for about 20 mins. I came to the first traffic light and noticed that the car started to run rough when stopped. Almost like it was stumbling/rumbling feeling. When I hit the gas it would bog down or stumble like you would think that it would stall but did not do so as I applied more throttle and got it going. If I let off the gas it would not stall but it had that feeling. Every traffic light after that did the same thing. I have been able to replicate the problem on every drive since. Starts up and runs fine then once it is warmed up it runs rougher. Any ideas what I should check? Carbs were rebuilt, new wires, distributor, fuel pump and filters were also replaced. Thanks in advance.