Weird Rattling when Accel. past 20ish

[BogeyBoy82]

2001 Tahoe...When im crusin at like more than 20...usually notice it around 35...let off the gas..then step on it again...i can hear a sound that resembles a header leak/blown gasket...to type the sound...tat tat tat tat tat...(haha)...had blown head gasket on my 5.9 grand Cherokee its similar... Im pretty sure its not the Magna-Flow doin it...any I'm scared to take it to the stealership b/c all the custom work ive been doin lately....any ideas???  thanks...

[carguru]

Sounds a lot like the exhaust gasket.  Did you put headers on?  If the exhaust manifold is stock, the dealer should replace those under warranty if you are under the 36k miles.  You should be able to have someone help you bring up the revs while in park (1000-1500 rpm) while you listen for the sound under the hood.

[5.3LSilverado01]

I sometimes hear a similar "rattle" under low rpm full throtle acceloration, but only with the a/c on. But I sometimes hear the same sound at highway cruising. It sounds like something rattling in the wind... I sometimes think its that rubber flap over the hood hinge flapping up and down. Thats where it sounds like its coming from... Any ideas? Whats that "fuel ball rattling around (or something like that)" thing I've heard about?