Q: white smoke coming from exhaust

White smoke on start up is typically due to steam clouds, that is condensation in the engine and exhaust vaporizing. Only if the white smoke doesn’t go away as the engine warms up and/or if this white smoke in the exhaust is accompanied by coolant loss is there anything to worry about. If there is coolant in the exhaust that, of course, would signify a head gasket leak, cracked block or like serious problem. Malfunctions in the brake booster cannot affect the engine, unless the malfunction creates an engine vacuum leak and even if such a leak existed, it wouldn’t affect the level or type of "smoke" in the exhaust. As far as the brake booster is concerned, that should be diagnosed as it may or may not be a cause of the brake fault you are describing. On a vehicle of this age, it would be desirable to have the entire brake system evaluated, of course, with an eye to fixing all faults. Brakes are important. To schedule a complete brake system inspection, the recommended service is a brake safety inspection.