tapping on gas pedal

Pretty much what the title says.

Especially when I take off from a standstill, and sometimes when I'm going down a bumpy road there is a tapping I can feel through the gas pedal.

I can't really hear it, and I don't feel it through the seats or anything else.

My current theories are the exhaust or motor mounts. I've never heard of anyone mentioning failed motor mounts, so when I crawl under the truck tomorrow the exhaust will be getting a close inspection.

Anyone ever had similar symptoms?