This is a problem a friend is having with her 3.1 Camaro. She's over 4 hours away so I can't just go round easily so I'm trying to get an idea of what could be going on.

She starts the car and the rpms sit pretty high even after the car has warmed up a bit. If she puts it in drive the rpms come crashing down and the car feels like it's about to cut out.

If she starts driving the car does indeed cut out!

My first thoughts could be the TPS? Or vacuum leaks. She can't read the codes or anything which doesn't help me either lol

 

Check the timing first, but make sure you unplug the Distributor disconnect on the firewall. If the Disconnect isn't disconnected, the timing will be off by several degrees.
Also note, the #1 cylinder on the V6 is on the opposite side than a Small Block Chevy. As you are in England, I cannot identify the sides as Driver or Passenger, so it's best to check which cylinder is the leading cylinder. (Note, if the battery is in the same location as a North American 3.1 Camaro, it is generally easier to time the engine utilizing the #4 spark plug wire. This prevents the timing light pickup wire from crossing the serpentine system. As #4 cylinder fires 360 degrees out from #1 cylinder, the readings on the balancer will be the same.)

 

FWIW, this was one of the first same exact problems I had to diagnose and fix on my 3.1 years ago. Turned out there was a 2-3 cm hole in a vacuum line that ran up to the injector assembly at the top of the engine — it was hard to find but once I replaced that line (among others) this went away.

Tell your friend to run her hands along ever vacuum line that she can see, using a flashlight to check for holes and cracks. In particular, any lines which might make consistent contact with the engine because of how they’re routed.

Not sure if this is the *only* problem but you’ll find this is one of the most common solutions which is easy to diagnose with some time. Good luck!