As soon as you take your foot off the gas, the throttle valve(s) closes and the boost pressure tries to escape via the compressor. But this leads to damage to the compressor and that is expensive. A blow-off releases the excess boost pressure with the characteristic hissing sound, thus preventing damage to the turbo. Using cheap blow-offs can lead to undesirable effects. Either boost pressure is already lost when it should actually go into the combustion chamber. Or it won't open and the turbo will be damaged. Our blow-offs from TIAL and NUKE PERFORMANCE impress with the best quality, so that they always do their job reliably, even with very high boost pressures.