and disconnect the part that goes back into the intake, and plug that hole - now the vacuum is holding the valve open a bit, so its causing the air to go right into the atmosphere. The car begins to run rough because the system is no longer 'pressurized'... so to circumvent such issues, a stiff/adjustable spring will allow it to stay closed under idle vacuum, causing the system to stay pressurized, and the ECU should adapt accordingly - otherwise you're just having arrant amounts of air fluxuating out of the valve. For instance, if you take your forge valve, and unplug that one end - and put a stiff spring in the forge valve, and used washer's to help adjust when the valve opens (under how many hG's of vacuum) you could make the forge's work as a BOV - the downside to this as some of us were discussing last night, is unless you use a very stiff spring - and use washers or what not to compress the spring some more, you lose some piston travel on release which may or may not be bad. It still opens more than a stock BPV...

The car will run correctly though - a simple test is to open one end of your valve, and tape the end closed, you will notice that your idle will be perfect (do NOT make boost while you have the tape in place).

2001 MTM STG4 S4
2004 MB E55 AMG

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