Basically ive had my car in storage for about 4 months! ive take my whole exhaust of and decided to put it back on and start it! it now soundz like a tractor/ really really loud! does it just need a good run?
I would'nt say a good run will cure the problem. If i was you, i would jack the car up and turn the engine over, then get underneath the car and see if its blowing on the joints, if so have a look at the state of the gasket's between the joints (if there is any) maybe they could do with re-newing. Also if its still blowing on the joints, then use some exhaust paste on them to ensure a sealed joint. Basically mate, just keep trying things to cure it!
sounds like you forgot the gasket from the manifold .. this blows a gooun when its missing, but it could be anywhere. As above, jack up, (secure it with stands before getting under it!) start the engine and see where its coming from.