Ok, just starting to build my Evo, and before I do and what not. At what point should I upgrade the wastegate? Basically...how much boost can the stock one hold? Or is it just a good idea to replace that after IE: Stage 1.

Also, could someone explain to me what all the performance ratings mean. I really only understand what it does and why it's there. (IE: Wiki information on it.)

Any help would be great.

 

Your stock WGA should be good for controlling 22-24 PSI boost levels. Beyond that level you might wanna look into a Forge HD WGA.

 

Hmm...cool. So how does spring rates affect the wastegates? Does it create higher tension inside the waste gate which in returns up the ammouint of PSi it can hold?