Hey y'all!

I recently purchased a 1994 945 Turbo, and it's been sitting since I purchased it.

Here's the issue: When starting the car, it idles SUPER rough, and sometimes dies. When revving it up to around 2k RPM's after starting, it will get a bit more smooth once it settles back down to around 800ish RPM's, but the idle is still choppy. Here's a video I took for an example:
Here's a list of the parts I've replaced: MAF sensor & intake box (from a pick-n-pull), spark plugs, distributor cap (from a pick-n-pull), coolant temperature sensor. Previous owner has receipts for the following work being done: fuel pump, fuel filter, fuel injection relay, & crank sensor. I also replaced the hard plastic evap hose (part 949701) from the intake to under the intake manifold with a rubber hose.

Other things I've done: Confirmed engine is in timing, cleaned the throttle body, cleaned the idle air control valve, added seafoam to the gastank and crankcase, did a compression test and got 160 on all cylinders except one (which was at 155).

Current known issues:
1. There is currently a very large exhaust leak at the downpipe to turbo connection. An exhaust shop said they think the cat is plugged and it will need a new exhaust from the downpipe back (So everything except the exhaust manifold & turbo). They also stated it'd be smart to replace my O2 sensor, as that's potentially fouled due to the cat being plugged. I'm unsure if this would cause the issue that I'm experiencing. I was quoted $1500 for a full replacement. I'll do it if that'll make my car drive-able, but don't want to drop that on a non-drive-able car.
2. My throttle body gasket is cracked, and I'll replace that shortly. Don't think that's causing my issue though.
3. There's a ground connection in the front right of my engine bay next to the battery that is disconnected. I tried grounding it, but it didn't seem to change anything.

I've tried looking for air leaks, and I haven't found any aside from the evap hose I replaced. I'm not 100% sure where all the lines are, but I've checked all the rubber hoses I've been able to find, and I don't see any leaks on the intake/exhaust manifold.

I also provided a screenshot of the evap hose I referenced for clarify/further information.

I'd appreciate any help, as I'm getting a little lost and losing a lot of hope. I don't want to have to give up on this car.

Thank you!

Evap hose I referenced (not my engine bay)

 

Here's how to check if the cat is plugged -
And here's how to clean it -
Also, if your throttle body gasket is cracked that could leak on and off depending on engine temperature. Which is why you probably didn't find it when you checked. I'd replace that first.