HKS EVC Boost Controller - install questions

[GTaaargh]

Hi.

My GTR had an HKS Mk IV Electronic Valve Controller, and the the servo motor is fitted flat - ie all hoses are on the same level. The installation instructions say ports 1, 2 and 3 must be on top, and port 4 on the bottom. They use the word 'must'.

Q1: Any idea why it 'must' be vertical, and if there are any consequences to having it flat?

Q2: Any idea what port 4 is for?

Trivia point: The sticker on the back of the EVC says it is a MK VII, but there is no such thing on the HKS web site. The part number on the inside of the Japanese manual matches with the part number on the MK IV documentation.

Thx.

[GTaaargh]

Bump. Still interested.