i have a 03 volvo s60 t5 manual, im looking into putting a BOV but i know there are complications because of the Mass Air Flow sensor. i was wondering exactly how bad is it to put a BOV on? or if there are systems that sound like a BOV that reroute air back to the intake.

 

Ok. I have a 04 2.5t and I did alot of resaech on the factory turbo. This turbo does have a factory bov built in. That being said you can disconnect that factory bov but you dont want to because it does reroute air back into the system. What I did was buy a cold air intake and then you release the sound of the factory bov.
If you put on an aftermarket bov you WILL loose horsepower. Also My cold air intake sounds bad *** when I shift

 

This man is 100% correct the Compressor by pass valve work the same way as a BOV and with a Volvo the blow boost pressure is re circulated back in to the engine and is always there when the ECU calls for it. Go for a hi-flow intake and like what ^ said you get the same whoosh sound with out the negative impact on performance
http://www.eurosporttuning.ca/mm5/me...Code=VL-S60-en
use this as a guide and build you own you need to measure the MAF and buy a cone filter that size then use the stock air box with no top on it. Or you can make a heat shield from a piece of sheet metal I have the EST and its works great but the $199 is a little much for what can be made for $75 or less GL