So my 1999 VW New Beetle sounds like a motorcycle when you start it up and idling it sounds like a lawnmower, and that increases when you step on the gas. Any ideas on what this could be? My dad is confident he can fix it, but he doesn’t really know where to start. He’s been reading the Chilton book like crazy, nothing yet.
Edit: this is after getting over $1,000 worth of work done 4 months ago.
It sounds like you need exhaust system work. If you’re lucky its just a muffler.
Your dad won’t likely be fixing this, depending on what the exact problem is.
What did you spend $1000 on?
a laundry list of things including fixing a cracked manifold. New development: while we were running it a bunch of insulation came out, and I mean a bunch. So we’re up under it right now looking at the catalytic converter. 
Is the check engine light on? If not, I doubt that it is the catalytic converter. Insulation - sounds more like it could be the muffler to me…but what do I know?
A bunch of what kind of insulation came out of where?
If your original manifold had a crack that was repaired, there’s a good chance that the repair has failed.
The insulation I bet came out of the muffler. Was the manifold replaced or repaired? The catalytic converter does not have insulation in it.