I have seen in this forum and experimented it by my own SUV a 1995 Montero SR 6G74 engine with 230,000 miles, that this engine has serious smoke issues at every mileage. My SUV if I have the right engine oil level and leave it for about half a minute at idle speed It starts to smoke and smell (oil burning)like a hell. I haven't had time to dismantle the engine and look for the possible cause of it but I think that it can be or piston rings or oil seals, but searching for possible clues in this forum I readed something about a PCV valve.
Where can I start checking the cause of this oil burning?
Is there anything else in this engine that can cause this oil burning? Why does it burn oil only at idle speed? The first 1.5 liters of oil it burns it very quickly when at idle speed, then when the level of oil drops to about 3 liters it quite smoking. Why? I hope there someone who can help me out?

Mine had similar symptoms. I changed the PCV but did not correct the oil consumption. It was only after I changed the Valve Seals that the excessive oil consumption stopped. In fact, it does not even use a liter of oil until the next oil change.
The engine ran smoother too after the Valve Seal change.
Hope this helps you.

It's a classic vavle seal problem, fairly painless fix <img src="/forums/images/graemlins/cheers.gif" alt="" />

Thanks for your answers.

Can I change the 24 valve seals without having to dismantle the engine heads. Is there something I need to know?

Yes, if you have about 40 hours to spare. I think someone posted a detailed procedure for your engine in the Mitsu Archive section.