Engine is missing on two cylinders but surges and kicks in

The first things I have always checked on GM anything with this issue are the spark plug wires, spark plugs, and fuel injectors; if it still has issues then I check the ignition coils (often not cheap on a Caddy or any luxury GM and it isn't a $20 part you throw at it and hope if you are knocking common issues out).

What makes it worse on your Caddy and any of these GM Northstars is they took notes from Germany on complexity and used 4 dual-plug ignition coils :-(. That explains why you are having issues with 2; if one has issues and it's on one specific coil, the other one has issues by default because the engine has to compensate on an engine with a complex ignition system. On a normal V8, you would only have trouble with the bad ones and you'd find it nearly instantly by feel once you know which side has the misfire. Once you know, you either swap coils or get a good code scanner and look for ignition coil codes. If you do not see a code then you can check the wire and plug as well as trying fuel system cleaner and an Italian tune-up, or both. By design, you can't easily do that on these dual-coil Northstars.

While it can be a deeper issue very often the issues you run into on a lot of older GM vehicles are that the spark plug wires are old and worn out, or the spark plugs are bad; sometimes both. Not quite sure if GM still makes them for this one and I very much doubt they do, but I know Auto Zone sells them (or if there's a "common" set that works on a lot of LT/Northstar V8s) if my memory is anything to go by when I had to look for a GMT800. Spark plug wires Ignition coil and spark plug set Ignition coil

If they both look good, then it may be dirty injectors given the limited miles; you can either try using a fuel system cleaner or just put your foot down and run the engine at a high RPM to burn off anything in the fuel injectors and piston causing issues; it may be a combination of the two being fuel injected. If they're really dirty this will help break down the mess in the injectors, but very often they require a proper cleaning if even using fuel system cleaner doesn't do the job.

While you can buy a machine to do the job on Amazon, it's not cheap for something you will use a few times. That said if you have a fancy car that is expensive to repair/maintain by default (especially a classic car) like an old German car I'd just buy the machine knowing the cost of repairs will make the machine worth owning. The ACDelco part for your Caddy is 19304542.