a lot of times with exhaust leaks u will barely hear it and then soon as u give it a little gas you'll hear it like a fluttering sound.

Mine was like that, it was in the header-to-downpipe connection.
btw, if anybody has a chikara header and blew that gasket, since they don't use the little rings like everyone else + oem does... here's what u do... go to advance and pick up a gasket for the 1988 nissan 300zx... and take a dremel and grind out the bolt holes a little to make them fit.

Put it in, torque to specs, voila. ;-) No waiting on Nopi to figure out how to get a gasket from chikara. ;-)

Harry