I just installed a hyperflow fmic. my problems is when i let off the gas at lets say 4000rps there is a shudder sound. it doese it at lower rpms also. ok let me explain it like this when i am going threw the gears it is fine but once i lift of the gas and not engage the cluch it like jerks 3 or 4 times amd make this shudder sound . it is all most like a a very old man clearing his throat. i have a gfb bov and i block of the return flow, that did not help it just made the blow off sound louder(fine wit me) when i did this i did notice that the valve was not very hard to push in, it is about 50% easier than the stock one. any respone will appreciated and welcome. all my mods are avcr,fmic,up-down-pipes,safcII(safc is for sale) short intake.

 

peole just leave a thought. it may be somthing i over looked.

 

yes I am using a 100% bov but it is making a wuffle sound and when I let off gas at higher revs it all most sounds like a metal wuffle sound. ok like if I am under the hood and give it gas and put my ear to the intake and let off it will make the sound but not loud,but the same sound, it is like a pulsing hollow sound if you can understand that. I am thinking my bov went bad or something is scraping

 

it is still making the sound after i bought another 2 bov's it make less sound with the ssqv the other bov i bought was turboxs. the turboxs is not worth the money it is very cheap.

 

wrong forum wrx boy

 

yes i can tune the bov's but that did not help at all

 

YOu're having a couple of problems. I assume that you're venting to atmosphere, so the hiccuping noise is what's known as reversion. Your BOV is too tight, so instead of blowing excess pressure out of the valve, it's hitting the valve and spinning your turbo backwards. After this happens, the only place for the air to go is out your intake filter. This causes the hollow noise. The shuddering can be caused by a couple of reasons. First, reversion disruptes the flow of air coming in, which causes your car to run rich. Secondly, Subaru's are designed to recirculate the air back to the intake instead of out into atmosphere. This also causes your car to run rich. Venting into atmosphere may sound cooler, but it hurts your cars performance.