Guys, need help on Custom clearance questions.

I always heard that RM500 is the maximum amount inclusive shipping cost if order things like Hobby Stuff from Japan if wanna escape the Custome Tax/Charges.

I also contacted the Custom at West Malaysia through phone just now and yes, it's RM500 on barang cukai.

However, last time when I ordered something from Hobbylink Japan on some gunpla, it went through well on West Malaysia custom.
FYI, the amount i ordered with shipping fee only around RM195.

But then when it reach my hometown at Miri, Sarawak @ East Malaysia, it was kenak tahan by Poslaju Custom and I went to Poslaju and asked them why?

They said policy different story in Sarawak and cannot exceed RM200 else 10% charge. I was like "what the!? "
Lucky my thing doesn't exceed RM200 and I can see from their reaction like "Aiyah, cannot receive some extra $$$".

So I need to find a proof for the custom policy on Sarawak so next time I won't kenak con again.
Anyone has any idea ?
I called the custom malaysia but they also like bo leng bo juak one, saying that they no idea and keep tell me story like reading from a script, no Sarawak Custom contact number ...