This is a simple modification but not as nice or as customizable as the dial a boost air valve.

Buy one spring from you local Pepboys or preferred store, below is the actual part number from Pepboys or you can get one similar and measure it like the picture below.

Insert the spring from the left side of the turbo to the right where the wastegate lies and attach it to the clamp on the wastegate on the intake side of the turbo unit.

Now attach the other end of the spring to the actual wastegate arm which controls the level of exhaust flow for boost.

The spring is the correct length and should be very close to 12 psi but again this is not as customizable as the dial a boost which I would recommend. Both are very cheap solutions and both work about the same for performance.