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Hi everyone, what is the port size for the FLP long tube headers? I prefer Mr. Gasket Ultra Seals personally.

Lastly would anyone know if the the FLP headers with the provided cats, hook up to the OEM exhaust or would I need to do modifications to hook it up? I have have dynomax intermediate pipes 2.5" in storage, but Im not ready to redo the exhaust since the factory is stainless steel.

I want to install the headers because I think I have a cracked passenger side manifold.
 

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The best way is to make a tracing of the exhaust port on the head, and one of the header flange. Compare them with the gasket to see if the gasket is at least as large as the exhaust port, and the flange is at least as large as the exhaust port. If they are both larger, you can use it without producing unwanted turbulent flow.
 

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FLP headers have 1 3/4" primary tubes. Best gaskets for a perfect fit are Remflex brand, part # 2007.

Their cats should connect to the stock exhaust location but the outlet size of the ball/socket is 2 1/2" where as the actual stock exhaust system is 2 1/4". It works, but the exhaust will be pushed back about a 1/4". Not usually a big deal because there is plenty of room with the small stock exhaust tubing. Just make sure to tighten the ball/socket nuts and bolts evenly so as not to create a gap on one side or the other.
 
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