fwiw posted by aliaZ on February 23, 2011 at 12:30 PM
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I think that once both manifolds are heat soated the thermal mass arguement is nullified. The issue becomes which one is radiating more heat out of the system. my guess would be the ss due to the large increase in surface area it has over the cast unit. Also the cast piece probably had smaller internal runners so off-throttle turbo responce would have been better.