I had bought a traxxasT

Question

i had bought a traxxasT maxx used today and was told it was a 3.3 and think its a 2.5 with a 3.3 engine how do i tell the differance or is the rest of the truck all the same.and seems to run very lean on idle and stalls or bogs when you go to take off it is a new engine 2 tanks burnt out of it