Was cleaning the mats today in my 85 300tdt and I noticed there is a button under the accelerator that gets pushed when the pedal is floored. What does it do. With the mats not fitting perfectly with age , I don't think the button gets pressed when I do floor it. Maybe I should correct that. I am assuming it has something to do with dropping the tranny down a gear? Sometimes my pick=up really sucks getting on the freeway.

Thanks

Peter