I'm looking to go with the Cork Sport catback exhaust on my 88 GTU, with an eye toward adding a Racing Beat header and presilencer within a few months. Will these pieces fit together? Will they be too loud? Can the rest of the exhaust be done easily later or should I do it all at once?

 

They will fit together, and yes it will be VERY loud.
These pieces all match up perfectly, so if you don't have the cash to do it all at once, you can piece it together over time.

 

How loud is very loud? I have a 1988 Mazda B2200 that I just run a header and Dynomax Ultraflow (basically a glorified glasspack) on and the sound doesn't bother me at all.

 

This setup would be MUCH louder than that. I have a 90 GTU with custom headers, gutted-cat, and stock mufflers and its still friggin' loud. Even idling its decently loud, and once you stomp on the throttle it roars. It doesn't bother me at all, but I think a lot of people would be bothered by it. Your setup would be even louder with after-market mufflers, although at the same time you'd have a presilencer, and I don't have one.

 

Well, let me put it this way - I've been known to drive around in wintertime with the window open so I can hear the exhaust note better in the B2200, and I plan trips so that I drive through as many tunnels as possible.

Right now I'm running the stock exhaust minus the driver's side muffler because it cracked and fell off. That's not too loud, it just sounds crappy at low RPM.