3 QUICK STEPS TO ADJUST A (BOV) BLOW OFF VALVE? - TurboSmart

Start with the BOV cap at the top soft position. Note: The edge of the cap should completely cover the indicator O-Ring.
With the engine at idle, the exhaust port should be closed off by the piston, and therefore the piston should be hard against the seat and not floating or moving.
Free rev the engine and back off quickly. However, the engine should return to average idle speed if the engine drops below idle or stalls. Go ahead and Increase the spring tension by one turn.
Repeat this process until the engine free revs and returns to average idle speed.
Test drive the car and ensure that the engine has minimal backfiring and no stalling when decelerating or changing gears. If you notice backfiring is excessive or stalling, check all connections made during the installation. Otherwise, increase the spring tension.

TECH TIP: BOV TROUBLESHOOTING

Firstly, check that the BOV is closed at idle if the BOV is not completed at idle. There’s a good chance the spring tension may need to be increased, or the BOV might need a heavy-duty spring.
Next, check the vacuum hose for splits, cracks, loose connection, kinking or any obstruction. It would be best to replace the old or tired hose’s, and it is also essential to know these hoses may collapse under a vacuum causing an obstruction.
Lastly, with the engine running, remove the vacuum/pressure hose from the nipple in the cap of the BOV. You should hear a loud hissing sound. The engine should idle poorly. Double-check by covering the end of the hose with your finger. If this does not occur, the hose could be blocked or crimped. Thoroughly check the hose and replace it if necessary.

First, ensure that the vacuum/pressure source is not shared and that the vacuum source is directly from the inlet manifold.
Next, check the seal between the adapter and the BOV – ensure that there is no gap between the BOV base and the weld flange.
Lastly, check the join between the adapter and the intercooler pipe for leaking.