If you have both available, I would opt for the Trust extension given that it provides you with increased oil capacity which is always a good thing, and has the modified pickup and baffle cylinder included.
I agree with MintR33 - For around the money they are asking when you take into account the cost of freight, you can pickup a Genuine Greddy Inlet Plenum kit - Much wiser option
The coil pack cover as I understand was briefly fitted to a car, possibly for demo purposes, the front timing cover is un-used.
The mark isn't big at all.
As I said, if you would like to make a genuine offer, flick me a pm.
Yeah, plus postage - And there are virtually none available in Japan
If you would like to make a realistic offer, send me a pm
Oh and by the way, 46000 JPY = $457 AUD
I have had endless pm's about them since I posted this earlier today.
The price is more than reasonable, and therefore firm, and the first person to arrange payment or pickup, owns them
Cheers.