Why is it so hard to find solid/concrete information from the government?

Yeah sure there are 2 paragraphs from DTI's website but that's about it. It seems like civilians offer more useful information than the goverment.

I'm moving to Makati in May and it will make me happy even if I can only bring one of my vehicles. The other, I'll just leave to my parents.

Which one is easier to import:

1999 Mercedes Benz ML 430
2004 Volvo XC90

Here's the part I don't understand... Why can't I find a chart or schedule or range that will estimate the duty of the vehicles, according to make, year, mileage, etc?

I don't mind paying duties as long as the terms are definitive. Any tips or any sort of enlightenment will be appreciated ;)