Hello everyone. This is a very niche question, but perhaps GT owners or mechanics can give me an answer. I’m looking to upgrade from the A1771420001 exhaust manifold found on most of our single scroll m177/m178 cars, and came across A1771420001T found seemingly only on the GT roadster. From what I see so far it seems slightly less restrictive, but it’s impossible to tell. Anybody know the difference? Maybe mechanics can judge on naming alone?. If not, any other suggestions for exhaust manifold upgrades? Modalworks has a beautiful solution I’ve been eyeing for months but 3.5k price tag is hard to justify.

Any contribution would be appreciated, you in advance!

To truly say one exhaust manifold design is "less restrictive / better performning" than another, we would need data: a direct A/B Comparison vs. the OEM, via flow bench studies, etc

Do we have any such data on the Modalworks unit, or other units? Their website on this specific product makes several claims, but none with actual data provided. . .

Interesting observation on the GT Roadster manifold - what property made it appear less restrictive? (have not seen one myself)