wastegate help needed

[99turbo2500]

I'm putting a 66mm on this week and plan on spraying it. I'm going to the the T4 gate plate to run the wastegate off. What size and type of wastegate should i get and where should i start at for getting the wastegate to open up before it builds too much boost? I'd like to limit the boost to 55lbs.

 

[TRM05]

38mm should be enough, but wouldnt hurt if you had the extra money to look at a 40mm or 44mm. some think its better to have more surface face for the gate... others dont agree. all i know is that my 38mm holds back my secondary really nicely.