I've got an 05 GSR. I had one previously for 10 years and am working on getting this"new" one up to speed.
Mods by previous owner.
Big injectors, FP White in stock housing (from YEARS ago but seems in great shape), ETS FMIC, Downpipe, exhuast, stock cat, stock o2 housing, stock exhaust manifold.

It had a knock off HKS BOV which I really didn't like. The previous owner included what I believe is an EVO X BOV, it's a metal one with the correct part number.
I ordered an ETS inter-cooler pipe kit and just finished putting it on.

A couple weeks ago I installed the "stock" BOV. I believe I installed it in the correct orientation based on some posts here, I installed it correctly (I think) horizontally, (Opposite the included picture). The car ran much smoother than with the VTA HKS knockoff which i expected but it was WAY down on power.

Cut to today, I installed all the intercooler pipes and the "stock" BOV. I went out for a drive and part throttle was fine but getting into boost the car didn't pull. When you floor it and it fully spools it starts making compressor surge noises and the boost gauge bounces (around 23 PSI) It also makes NO power.

I thought maybe I had installed the BOV backwards so I flipped it. (Attached image). With this orientation (i think this is backwards) the car pulls hard like it should BUT any part throttle acceleration is met with compressor surge and the full throttle lift BOV sound is like nothing I've ever heard. It's CLEARLY not right. It makes the normal woosh of a stock BOV but it also makes a REALLY loud siren noise for about half a second. Louder than the HKS by far.

I ran out of time to check if the BOV is actually actuating but it does hold positive and negative pressure on the boost signal port with a hand vacuum pump.

Any ideas? Attached image is the bonus FP white wheel in stock VIII housing, and the "stock" X BOV installed the wrong way, I think

X BOV in "wrong" orientation.




Old FP White, is this an VIII or IX housing?

 

try putting it on the right way and do a boost leak test.

 

So no boost leaks up to 30 PSI. BOV installed in the correct orentation.