This is a comparison of the 2G plastic BOV and the EVO IX's steel BOV. I hope this topic will give you enough info to make a choice for yourself.
My factory original, 20 year old, 145,000 KM, plastic BOV was leaking air at 6 psi (BrettH completed a pressure check between my turbo & intake manifold). I wanted to keep my stock UICP and did not want to bother with a 1G adapter to fit a 1G BOV to my UICP. For my application, I went with the EVO IX BOV vs. the 1G BOV that comes highly recommended. The EVO IX's part number is 1545A001 (1545A001, written twice to reduce typographical errors) and a new one cost me US$101 plus shipping.
Observations:
My seat of the pants dyno told me the UICP was holding more pressure.
There are no strange sounds from this BOV. It sounds the same as my old, plastic one.
The EVO IX BOV stands a little taller than the plastic BOV, but it does not touch the under side of my hood. I put a piece of crushable foam between the top of the steel BOV and and my hood, and then shut the hood. The foam crushed down to 3/8" - 1/2".
The vacuum hose is at 3 o'clock vs. the steel's 11 o'clock orientation. Make sure the hose does not kink after installation! Better yet, replace that rubber vacuum hose with a thicker walled, silicone vacuum hose.
Dimensions, please see pics:Inlet diameter
Outlet diameter
Overall height
Overall width
All steel construction
For additional research, some references from other DSMers:
http://www.dsmtalk.com/forums/showthread.php?t=161635&highlight=evo+bov&page=2http://www.evolutionm.net/forums/evo-engine-turbo-drivetrain/24611-blow-off-valve-testing-really-works-2.htmlhttp://www.dsmtalk.com/forums/showthread.php?t=232815&highlight=evo+bov
