Gambba is right. Unless you know what you are doing, fitting a diverter valve that dumps to atmosphere will give you problems.
Personally I wouldn't waste your money. I ran two Hyperboost valves on my AMD chipped S4 (£170). The Hyperboost are virtually identical to Forge's design. (In fact it's a wonder Forge didn't sue!) The current piston type valves will never be as efficient at dumping/diverting the air as quickly as the Bosch units which are a diaphram design. Like you want too I followed the sheep thing which I also nearly did with the exhaust CAT back system to until I learned better. The Bosch DV is cheaper and more efficent but is known to tear. Buy two and check it from time to time.
If you must buy a forge type valve gives us your thoughts on whether you notice a difference. Have a mate fit a Bosch unit and a piston type, see if you can tell. A lad on Audi world did this with two types of piston valve and the Bosch unit. He couldn't tell the difference!