What can be causing a loud pop out the end of my exhaust pipe. It's a Chevy 400. It does it at idle and when I let off the gas after reving it. At idle it does it every 30 sec. or so. Also has alot of condensation out pipes at start up. I forgot to mention it's a Quadrajet. It starts and idles good A little on the fast idle side.

Thanks

Ralph