How can you tell if you have a faulty n75 valve

 

If I remember rightly disconnect the N75 and measure the resistance between the contacts on the valve. I think the value should be above 15Ω if it isn't the valve is faulty. Hopefully someone else can confirm this.

Just had a chance to check it should register between 14 -20Ω you may need to unbolt it to get access to the terminals. Good Luck

Sorry about this but I found out earlier the range should be 25Ω to 45Ω. Mine reads 15.8 so will be changing it as it might be part of my boost problem. Apologies for the incorrect info.