Accelerator Stuck problems of the 2000 Mercury Cougar

My vehicle has not caused an accident or a crash yet, but it soon could. The throttle/ accelerator has been sticking on my 2000 Mercury Cougar since soon after I bought it in October of 2003. It started with the rpms revving up to 2 or 3 as I was coming to a stop. This happened once every couple weeks or so. The rpms do not go down until after I have completely stopped. It has since became more frequent (close to every time I drive the car) and significant(rpms go to 3 or 4). I took it to the Lincoln Mercury dealership soon after I first noticed the problem in April 2003. They repaired a blown air valve. The problem began again within a month of the repair. I then took it back in June 2003 and reported the same problem. They cleaned the throttle. However, the problem began again within the next month. In may 2004 I received a recall notice for a contaminated fuel pump. Thinking this was the source of the problems I had the fuel pump replaced. The problem began again within a month. Not being able to afford to put more money into my car, I waited a year before taking it to the dealership again. Upon emissions inspection in September 2005 they failed it because the check engine light was on. I took it back a week later and they passed it. The light was off then. It has been going on and off on its own since I purchased the vehicle. Recently while driving the accelerator stuck making my car stay at 40 mph even though my foot was not on the gas. I researched a 1999 recall that seems to fit the exact description of my cars problem, but Ford insists that couldn't be possible.