I've come across three different part numbers for the stock boost lines w/boost pills.

MN143555
MN156396
1632A117

When I check any parts website they have different prices as well. Are there differences between each hose assembly?

 

The two top #'s are the same ones that I came up with. I'd double check with the dealer as well.

 

I dont know the number, but u can get it here. Just scroll half way down the page.
http://www.mitsubishiparts.net/catalog/?section=1073

 

Based on that link and checking the prices it seems the first parts number is correct for the 03 Evo 8. i will check the the local dealership, but they're about as useful as a wet fart.

 

Your first hunch was right....MN143555.