An air leak anywhere between the engine intake and the mass air flow sensor is often called a 'vacuum leak' or 'intake leak'. Common examples of vacuum leaks include a ripped or cracked intake boot, leakingintake manifold gaskets, stuck-open or defective PCV valve or ripped PCV hose, crack...
A bit of oil in thethrottle body is not going to harm your motor and is certainly not going to cause it to blow up. At an idle, the PCV valve restricts air flow, to reduce this problem. ... The flow of air draws fumes from the crankcase and burns them harmlessly in the engine....
Engines with excessive blowby will sometimes fill the air cleaner with oil: there's more blowby than the PCV valve can handle so the blowby gas goes backwards into the air cleaner. A lot of cars have a broken PCV inlet hose: those cars are SUCKING DIRT AND DUST INTO THEIR ENGINE!!!
If the engine runs hot at low speeds or at stops I would be suspect of a faulty radiator cooling fan motor which is not coming on. OR, there is an air bubble in the cooling system that needs to be bled out. If you did not have this overheating issue before the radiator hose replace...