2000 Mazda 626 blows light white smoke

2000 Mazda 626 blows light white smoke after reaching 50mph

I have 2000 Mazda 626 that has been sitting for a few months.. The car runs and starts good no lights on panel on.. The battery has been disconnect since it hasn't been in use.. from time to time i start it and move it.. all fluids are full no leaks. Belts have been changed fluids as well. I have noticed once the car reaches 50mph the car will begin to blow light white smoke from tail pipe.. It stops blowing smoke when the car is idling. No other problems so far. I was told it could be Throttle Body need to cleaned.. but when I think of smoke coming out it leads to head gasket... Mechanic said it needed to be reprogrammed.. Unsure what that has to do with the smoke..

Basically it needs tuning and / or cleaning, you can a try an Internal Engine Cleaner Crc Motor Treatment 16 6.55 eBay. and see if that helps, i understand your worries about the headgasket of water problems, the best way to tell is to take your oil cover off the engine and look for a white substance (mayonaise) if its black or brown its just oil and all is good, but if it is creamy white or going that way then oil has mixed with water and you may have a problem, but with it been white smoke (not to mistaken with steam) then it's prob just a tuning issue.