Ext. Wastegate Question (please help)

I'm in a delema. I'm not sure what external wastegate to get Tial 38mm or Tial 40mm. What's the advantage/disadvantage of both. Also, I'm open for other suggestions......
My relating mods are:
-Evo 3 Big 16G
-custom o2 housing
-3" Turbo back
-Test pipe instaed of cat
-Turbosmart MBC

Both should give you what you need for your turbo. The tial 38mm has a diamond-shaped flange, whereas the 40mm has a square-looking flange. If you're looking for a 40mm I have one used that you can buy, but you'd have to get the square flange yourself that you`ll need to weld onto whatever header/manifold you`ll be using.

38mm will do fine, and is cheaper than the 40mm. I run a 38mm with a 57 trim T04E. No creep issues for me.

Thanks for the feed back. I'm leaning towards the 38mm