Vibration in gas pedal

I just recently had a 6 inch lift installed on my 2013 Tacoma . Everything went well as far as I know but when I get around 50-70 mph there is a weird vibration in the gas pedal. When it happens it lasts for a few seconds goes away for a few more and then comes right back and continues like this. I know the tires aren’t out of balance and they are brand new. I tried to read up on it on other forums but no one described it exactly like mine feels. Any help is appreciated.

 

This is the truck

 

It sounds like your lift (or new tires) has introduced a harmonic vibration, (felt through the gas pedal?) since it wasn't there before. Since the gas pedal is bolted to the firewall and connected electrically to the throttle body, you are likely feeling a vibration from the driveline (or tires) through the floor of the cab. I'm guessing the changes to your driveline angles (or tire balance) need to be checked. There are literally hundreds of posts on TW regarding vibrations after lifts.