Sard R2D2 Racing Blow Off Valve is really great looks cool and makes really loud pssssh sound and can be adjusted to how fast you want it to vent. It is very reasonable too only paid 170USD.
The custom downpipe was a project I did not want to do. cause I ordered a front pipe from HKS and it replaced only the main cat, they should have mentioned midpipe. Anyways I had to make a front pipe from the turbo manifold to the midpipe flange with O2 sensor to eleminate my precat. Real bummer!!
The Jap turbo exit manifold is only a little over 2 1/2" wide so the pipe made was that size till it hit the midpipe which was 3". made it in Stainless steel and was polished too! not necessary but the guy who made it just wanted to impress me with his work. Also the Priest exhaust is 4" with 5" tip.