carb balancing?

just recently the bus has started to spit back through the carbs a bit at about 1/3 throttle. does it when cold a fair bit too. so would i be right in thinking the carbs need balancing or they have got some shit stuck somewhere. so a bit of redex maybe or summat along them lines?

cheers guys.

blown inlet manifold to head gasket . piece o piss and only 80p.
happy days.

Cool . Balancing carbs is beoned me

all happy now