I did the single spring mod for the Greddy type-S (using the larger spring) and at idle my BOV was whistling. So I placed my hand in the vent and could feel air coming from the UICP.

My understanding is that even with the vacuum from the intake, the BOV should remain closed under idle conditions, is this correct?

and if it is, is there a problem with my BOV?

 

okay, after some googling i have found that at idle the bov should be closed at idle and that the spring should give enough resistance to keep the valve closed.

but, according to instructions I have found for the single spring mod, they suggest only turning the set screw in 2-3 revolutions. it seems that I need to turn it much further than that to keep the valve closed . . .

anyone else with the type-s experience the same thing?

 

how about everyone stops doing the single spring mod.... read the end all bov thread for the reasons why.