Heat the manifold up internally with a hair dryer to tighten the wrinkles up a lot.
I had a hair dryer running for 45 mins through the throttle body hole & had the manifold stood off the ground on some dowels to let the hot air flow all the way through the manifold.

End result:

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[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]