I hear a swoosh/whistle and a drop in power past about 5,00RPM in my 2005 Evo 8, is this a bad BOV?

 

is what a bad BOV? you shouldn't be dumping into the atmosphere with a MAF, you need to recirculate it.

 

Sounds like its VTA (Vent to Air). You need ot look into if the current brand of BOV you have has a recirculating option and purchase that or just get rid of the BOV and replace it with something is made for the MAF setup of the Evo (recirculating).

 

I have the stock Evo 8 BOV and this problem just recently showed up. If the BOV fails what are the symptoms? Dumping into atmosphere? Sudden drop in boost?

 

Sounds more like a boost leak. Do a boost leak test. Probably one of your couplers are loose.

 

Buy the aps twin vent and forget bov problems. I've had them all this is the best

 

If you can't find an aps, get the synapse diverter valve.

 

If you ever plan on having an evo that actually runs properly...buy one of these, it will change your life.

http://boostpro.net/prodtester.html

You can make them yourself but these ones are nice and have the gauge for easy reference. The oem VIII DV is crap, so it may very well be the leak point. In all honesty you most likely have multiple leaks, so by fixing one you will inherently uncover the next leak point. I'm guessing you're a new owner, so do some searches on boost leak test methods.

Common leak points: Plastic oem DV, throttle body shaft seals (pretty much guaranteed unless previous owner replaced), injector ring seals, any IC piping couplers secured with worm-drive clamps.

Bet you thought owning an evo was gonna be all fun...welcome to EvoM