Thanks for the nice comment's everyone.
Yes, that is Roger Clark Motorsports Anti Surge Kit. Rather than the Bosch 044 pump it has the Bosch Motorsport pump for additional reliability.
The jump from 300 Bhp to 400 was a huge leap, but the jump from 400 to 500+ (in an Classic Impreza) is a different ball game. I was told that my driving method would need to change and they were so right.
Large gaps between cars don't work anymore, you need a completely clear road.
At 4000rpm it accelerates at the same rate in all six gears and you realise how quick it is when you glance down at your speed. If you hit the slightest bump, ridge, manhole or anything that is not flat (when on boost) you spend every second trying to keep the thug going straight.
For the first time the words "respect" & "right off" enter you head, very often.
At 400Bhp you can feel the car breaking away, at 500+ you don't, it happens extremely quickly.
Great crack though
Next up is a twin map and running on bio
