Yes, you will run rich. Not all the time necessarily, but definitely between shifts. A blow off valve in a vent-to-air configuration releases air that the MAF has already accounted for (and the ECU has provided fuel for). If you have a bunch of young guys in the area that throw a fart can and BOV on their Subarus, listen to what it sounds like when they drive away and shift. It usually stubbles, maybe with a little bit of popping from light backfires. Not good.
If you MUST have a VTA BOV, you do have options:
A good tuner can often correct for AFR changes from dumping boost to the atmosphere, instead of recirculating it (like the stock configuration).
So you could always inquire with a local tuner and see what they say BEFORE you just buy something. Seeing how you already have a couple mods, I would highly suggest seeing a tuner for a protune anyway. Thank God you're at least running a Cobb OTS map. I can't even tell you how many tools I see destroy their engines because they have 4-5 mods and still on the stock tune. Every engine related mod likely requires a retune just to be safe, let alone get the full power potential.
The factory bypass valve is actually a pretty damn good unit. If you were to ever had problems holding boost, maybe you'd crush the plenum a bit, but generally speaking the factory valve is more than enough for the stock turbo. AND it's actually pretty loud, even in recirc, but that depends on your intake. I see that you have a Cobb cold air intake. IMO that should make the valve considerably more audible than it was with the stock intake. (The valve returns the released boost back into the turbo inlet tube, which is why if your intake is large and open filtered so to speak, you can hear the valve noise escape from the air filter.
Back to tuning for a moment, you could go with a Speed Density configuration and tune, like Grinder said. You could also relocate the MAF sensor to be AFTER the valve. This would allow the valve to dump the released boost before any air metering is done. This is how I am configured and it's generally known as a Blow-Thru MAF. All this is far too much screwing around and waaaaay to much money just to have the VTA BOV sound.
I don't really know much about the Cobb XLE valve, but Cobb turns out good quality parts, so I would trust it. If you do decide to get it, I would suggest running it in Hybrid configuration (50% of released boost get's recirculated and 50% vents to the atmosphere). That would probably be your best bet when it comes to keeping your engine running decent (likely to be safe without a retune) AND give you that extra noise you are looking for.
Though in the end, I can't help but mention, this is a $300 part. If the sound is worth that much to you, you'll probably be fine getting the Cobb XLE. But for $300, I'd save up my money until I could install multiple power mods at the same time, at which point you could throw in a VTA BOV just for shits and giggles.
If that $300 is burning a hole in your pocket, may I direct your attention to suspension modifications. :lol: No really, I'm serious. Sway bars, end-links, polyurethane bushings, sway bar mounts and so forth...are all great low level mods that are fairly easy to do yourself, don't cost very much and offer a big performance increase per dollar compared to other mods.
So, if it were me, I'd spend that $300 on a Whiteline sway bar in a heart beat before I'd (sort of) waste it on that valve.
That's my best advice. Hopefully it doesn't ruffle your feathers. And by the way, welcome to the community! :tup:
