I should leave the pipe in the box where you found it, youd have to be going some to get a CVH 4/4 carb to ice up just with a K&N.
As for you throttle sticking,
check the cable is free and the inner slides smoothly in the outer, check the outer make sure the plastic covering is not melted,this could point to a poor engine earth,a common problem on Morgans, if this is the case change the cable and make good the earth points to the chassis, in the engine bay and at the battery.
Check the pedal isn't fouling any carpets, rubber trim on the inside of the scuttle etc.
make sure that the linkage at the carb end is free and nothing is fouling it.
hope this helps Jim
