I have a 1975 280Z and I am trying to find out the best way to improve performance and the exhaust note. It sounds like it is not easy to properly install a header without using several gaskets for the in-line 6 motor to avoid leakage. Please share any experience regarding this issue.

Those two things are not well-tied together. Straight pipes, no muffler, and a header, would give the "best" performance increase, although the total benefit fit might be small. The stock factory manifolds flow pretty well, apparently. But they might not have the sound you're looking for.

Post a link of an engine making the sound you're looking for, or describe it, and someone might be able to to tell you how to get there. It's very subjective.

A header is not an exhaust and vice versa. You don't need several gaskets to keep the header leak free. One good one with a proper installation works just fine.

I have the ceramic coated 6 to 1 header from MSA and their 2 1/2" premium exhaust, Felpro gasket off the shelf at local auto parts store, no leaks. I did use better manifold studs and exhaust locking nuts from a Nissan dealership. The exhaust and bigger wheels and tires are my 2 favorite purchases so far. It has a "screaming bloody murder" sound up high in the RPMs, like a sport bike. The exhaust was around $500, wheels and tires $700.

Hi Zed Head, John Coffey and site unseen,

Thanks for the replies and sharing your wisdom.

Zed Head, all I am looking for is that classic mellifluous Z exhaust note so it sounds like a sports car. I have heard that before about the factory exhaust manifolds flowing quite well so can this be achieved by enlarging exhaust and installing the right muffler?