I got this great truck that is unhappy at the moment. I am in Hawaii, that isn't why it is unhappy, I have been adding coolant/water more often than usual. My exhaust is a bit drippy and white. And when I am low on coolant it idles up and down up and down. I have all the paper work from the previous owner and all work was done at Toyota and the engine was rebuilt not too long ago. I don't see anything in the oil indicating a head gasket issue, or anywhere my coolant is leaking. Some friends say some of the follow, Thermostat (cause the heat isn't that hot, not that I would ever notice till I put it on to try to cool down the tuck) , put a small stick in the pan and see if it stops to check a fan clutch, could be a water pump, and maybe it is coolant getting into the engine area and spitting out the tailpipe, WHAT DO YOU GUYS SAY?

Petrol or Diesel ?

What's 'more than usual' ? I add coolant to mine maybe once a year.
If you adding coolant on a daily or weekly, even monthly basis you have a problem, it's going somewhere.

Do a compression leakdown test on the engine and a pressure test on the cooling system. Go from there.

It could be something as simple as the radiator cap, or more serious like a headgasket.
Since you don't seem to have an issue with coolant in the oil or oil in the coolant, it's probably not a worn Timing Chain wearing a hole thru the TC cover.

It sounds like a head gasket is leaking into a cylinder. That's why you are getting white steam out the exhaust. Pull the plugs and see if once looks like it's been steamed cleaned. A leak down test would be good too.