I have question for you mbx-5 guys. I just bought a new mbx-5 prospec. Is there anything that needs to be upgraded or should i just leave it alone? Next what is the most commonly broken parts that I should carry with me..

no and none, but a pair of front lower arm just in case for bashing

NOPE! It's perfect the way it is! just spare parts, for just incase you have a very hard impact! Glad to see another MBX-5 Pro Owner, you'll enjoy

lower arm, hub carrier knuckle and front shock shaft.

if ur buggy hit often, check the shock shim and replace once it loosen