Rattle feeling on Gas pedal HELP?

[LRB]

I have a 05 LR3 v8 and under acceleration when rpms get high like before a shift I feel a rattle sensation in the gas pedal as if something under the truck is shaking. Only happens for a second or two then goes away as soon as it shifts to 2nd and rpms go down. Does not happen every time mabe once a day. Might be worse when I have some pressure left or right on the steering wheel. I do not hear it just feel it. Could it be a loose exhaust system...It has been going on the last 30k miles and I have 70k now. I am bringing it in for a/c whine noise tommorow and want them to look at that as well. ANY IDEAS??? Also does anyone know exactly what they do to fix Farting noise a/c makes when its turned on and off. ?Thanks.