Have just purchased what appears to be a well maintained Series 2. Picked the car up yesterday and drove ~ 250 miles at an average speed of 55 mph. Car ran well on the main roads. However, when I got into local traffic closer to home the throttle sticks open somewhere in 1500 - 2500 rpm range. If I blip the throttle hard, sometimes I have to do it 2 or 3 times it comes down to the 900 or so level. The previous owner had rebuilt the carbs and when putting the engine under load it responds well. I checked the oil in dash pots and the level looks correct, I get resistance when putting the piston back in.

Appreciate any help or guidance anyone can provide.