Why would the throttle on your 2000 Ford Focus be sticking?
the reason the throttle would be sticking on your focus is that it (the actual unit) could be dirty. or the throttle cable could have dirt in its casing. what you need too do is remove the throttle cable and spray engine degreaser in the casing and hang it up too let the dirt and grime drip from it. be sure to use wd-40 to relubricate the cable. now as of the throttle body do the same thing. but use a non abrasive cloth and wipe the unit clean. make sure there is no dirt in any small cracks or crevises.
If you recently changed the spark plugs on your 2000 Ford Focus and now the throttle is sticking is there any relationship between the two?
I can tell you with relative certainty that the condition and/or operation of the spark plugs should have nothing to do with a sticking throttle. Your best bet would be to check your throttle body for buildup or debris. Also you might check the throttle return spring on the side of the throttle body.