Speed Control Cable problems of the 2010 Ford Ranger

Accelerating up hill throttle locked into full open (full throttle) after reaching level grade. Brakes barely able to restrain truck. Got stopped and into neutral at side of road. Throttle stuck open at 3500 to 4000 rpm. Throttle cable able to be returned to idle manually from engine compartment. Able to repeat lock up by "goosing" accelerator (this after second occurrence). This is used commercial vehicle. There is no carpeting. No codes or other explanation recorded by vehicle computer. First occurrence, mechanic ascribed to loss of air intake due to mouse nest in airbox, with vehicle computer causing acceleration. Likely wrong, likely same as second occurrence. Second occurrence, mechanic ascribed to throttle body carbon deposits resulting in binding of the throttle linkage (no mouse nest present). Cleaned throttle body. Have about 20 miles on truck since cleaning. Assuming carbon build-up explanation proves correct, this is a serious condition to have happen due to normal wear at relatively low miles.